Method of fabricating a semiconductor device

ABSTRACT

In a manufacturing process of a semiconductor device using a substrate having low heat resistance, such as a class substrate, there is provided a method of efficiently carrying out crystallization of a semiconductor film and gettering treatment of a catalytic element used for the crystallization by a heating treatment in a short time without deforming the substrate. A heating treatment method of the present invention is characterized in that a light source is controlled in a pulsed manner to irradiate a semiconductor film, so that a heating treatment of the semiconductor film is efficiently carried out in a short time, and damage of the substrate due to heat is prevented.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of fabricating a semiconductordevice including a circuit formed of a thin film transistor (hereinafterreferred to as a TFT) using a crystalline semiconductor film formed on asubstrate having an insulating surface. Particularly, the presentinvention relates to a liquid crystal display device in which a pixelportion and a driving circuit provided at its periphery are provided onthe same substrate and an electrical instrument (called electronicapparatus as well) using the liquid crystal display device as a displayportion.

2. Description of the Related Art

With the rapid development of an information-oriented society,information appliances including a personal computer (PC) rapidly becomepopular for not only a business enterprise but also an individual. Fromthe viewpoint of space saving of portable information equipment or adisplay of the PC, a liquid crystal display device (liquid crystaldisplay) is regarded as being promising from the early days. However,there has been a problem that a manufacturing process of the liquidcrystal display device is complicated and its yield is low, andaccordingly, manufacturing costs are high.

Besides, in recent years, from a problem of a field effect mobility,technical development of a thin film transistor (hereinafter referred toas a TFT) using a polycrystalline semiconductor film, for example,silicon as semiconductor (hereinafter referred to as a polysilicon filmor a crystalline silicon film), which has a polycrystalline stateobtained by crystallizing a noncrystalline semiconductor film(hereinafter referred to as an amorphous silicon film) formed on aninsulating surface provided on a substrate (for example, a glasssubstrate, a quartz substrate, a stainless steel substrate, etc.), hasbeen rapidly advanced. Especially, a polycrystalline silicon filmprepared by carrying out a heating treatment for crystallization at alow temperature (600° C. or lower) is called a low temperaturepolysilicon film.

In recent years, researches have been carried out to construct asemiconductor circuit by forming TFTs on a lass substrate or the like.As an electric device such a semiconductor circuit, an electro-opticdevice such as an active matrix type liquid crystal display device istypical.

The active matrix type liquid crystal display device is a monolithicdisplay device in which a pixel matrix circuit and a driver circuit areprovided over the same substrate. Further, the development of asystem-on-panel having a built-in logic circuit, such as a memorycircuit or a clock generating circuit, has also been advanced.

Since such a driver circuit or a logic circuit requires performing ahigh speed operation, it is unsuitable to use a noncrystalline siliconfilm (amorphous silicon film) as an active layer. Thus, in the presentcircumstances, a TFT including, a crystalline silicon film (polysiliconfilm) as an active layer has become mainstream.

Then, research and development has been actively carried out as to aprocess, a so-called low temperature process, for forming a large areacrystalline silicon film on a substrate having low heat resistance ascompared with a quartz substrate, such as a glass substrate.

As a method of preparing a low temperature polysilicon film, a laserannealing, method, an ion doping method, or the like is mainly used. Asa method of obtaining a high quality low temperature polysilicon film, atechnique using a metal element as a catalytic element for facilitatingcrystallization is disclosed in Japanese Patent Application Laid-openNo. Hei 7-183540, etc. As the metal element, nickel (Ni), palladium(Pd), lead (Pb), tin (Sn) or the like is used. The catalytic element isadded to a semiconductor (silicon) film by a method, such as a solutioncoating method, a sputtering method, an ion implantation method, anevaporation method, or a plasma treatment method, and a heatingtreatment for crystallization is carried out. However, there has been aproblem that although such a treatment can be carried out at a lowtemperature, a treatment time is long.

The present inventors et al. disclose a technique for obtaining acrystalline silicon film on a glass substrate in Japanese PatentApplication Laid-open No. Hei 7-130652. In the technique of theinvention, a catalytic element for facilitating crystallization is addedto an amorphous silicon film, and a heating treatment is carried out tocrystallize the amorphous silicon film.

By this crystallization technique, it became possible to lower thecrystallization temperature of the amorphous silicon film by 50 to 100°C., and to shorten a time required for crystallization by a factor of ⅕to {fraction (1/10)}. As a result, it became possible to form a largearea crystallized silicon film even on a glass substrate having low heatresistance. It is experimentally confirmed that the crystalline siliconfilm obtained by such a low temperature process has excellentcrystallinity.

Besides, an environmental problem becomes more serious, and it isemergently required to take energy-saving measures with respect toelectric appliances at worldwide level. Then, in order to achieve suchan object as improvement of efficiency of a manufacturing process formass production of liquid crystal cells or reduction of manufacturingcosts, enlargement of a substrate in the manufacturing process isrequired, and technical development for obtaining a plurality of TFTsubstrates from a large glass substrate has been advanced.

Incidentally, in the present specification, the liquid crystal cellindicates a display device in a state where a liquid crystal isinterposed between a substrate on which pixel TFTs are formed and acounter substrate.

The present applicant discloses, in Japanese Patent ApplicationLaid-open No. Hei 7-130652, a method of fabricate a crystallinesemiconductor film having high crystallinity by adding a metal element(hereinafter referred to as a catalytic element) having a function offacilitating crystallization to an amorphous semiconductor film in acrystallization step and by carrying out a heating treatment.

However, the method of the above invention is a heating treatment usinga furnace, and it takes a rather long time, for example, 1 to 14 hoursto carry out the heating treatment and to form the crystallinesemiconductor film.

In the manufacturing process for actually mass-producing semiconductordevices, shortening of a treatment time is an important problem.Besides, as another technique for improving the efficiency of themanufacturing process, the establishment of a technique of manufacturinga plurality of liquid crystal cells, for example, six liquid crystalcells each having a size of 12.1 inches from one large glass substrate,for example, a substrate of 550 mm×650 mm has also been advanced. Infuture, a technique and a manufacturing, apparatus for manufacturingmore liquid crystal cells from a larger glass substrate are required tobe introduced. With the enlargement of another member (glass substrate)before treatment, an apparatus used for the manufacturing process isnaturally required to be enlarged, and a furnace for carrying out theheating treatment has a problem on the enlargement of an installationarea, and needs energy for uniformly and sufficiently heating the largefurnace for treating the large substrate as set forth above, and therehas been a problem that the energy becomes enormous electric powerconsumption.

Then, in view of the efficiency of manufacture and the improvement ofproductivity, it is conceivable that an RTA (Rapid Thermal Anneal)method is suitable as a heating method. However, the RTA method is amethod in which a heating treatment of a high temperature and a shorttime is carried out for the purpose of suppressing the diffusion of animpurity in a semiconductor layer, and in a heating treatment step of asemiconductor film requiring the diffusion of an element, such as acrystallization step using a catalytic element or a gettering step,there is a possibility that a glass substrate is distorted before adesired effect is obtained. For example, it is confirmed that in thegettering step in a furnace, the glass substrate is curved and deformedby its own weight by merely carrying out a treatment at 800° C. for 60seconds.

SUMMARY OF THE INVENTION

An object of the present invention is therefore to solve the aboveproblems and to provide a method of efficiently fabricating an excellentcrystalline semiconductor film on a large glass substrate in order toenable mass production using a large substrate.

It is known that when a heating treatment is carried out in a hightemperature state exceeding 600° C., high speed growth of an oxidizedsemiconductor film due to a catalytic element occurs, and breakdown of aformed semiconductor component occurs. Further, it is known that when aheating treatment is carried out in a high temperature state exceeding900° C., an oxidized semiconductor film grows at high speed even in aregion where a catalytic element is not contained.

Another object of the present invention is therefore to shorten a timerequired for a process by controlling a light source to irradiate apulsed light in a heating treatment for crystallization.

Still another object of the present invention is to reduce hydrogen in afilm to improve crystallinity by carrying out a heating treatment forcrystallization in a reduced pressure atmosphere. Besides, still anotherobject of the present invention is to reduce an oxygen concentration inan atmosphere and to suppress formation of an oxide of a catalyticelement for facilitating crystallization by carrying out a heatingtreatment in a reduced pressure atmosphere. Besides, still anotherobject of the present invention is to facilitate crystallization and toshorten a crystallization time by carrying out a heating treatment forcrystallization under vacuum. Besides, still another object of thepresent invention is to reduce hydrogen in a film and to improvecrystallinity by carrying out a heating treatment for crystallizationunder vacuum. Besides, still another object of the present invention isto reduce an oxygen concentration in an atmosphere and to suppressformation of an oxide of a catalytic element for facilitatingcrystallization by carrying out a heating treatment under vacuum.

If a catalytic element at a high concentration remains in asemiconductor film after an excellent crystalline semiconductor film isfabricated on a glass substrate by a low temperature process, thecatalytic element forms a deep energy level in the semiconductor film(silicon film) and traps a carrier and is recombined. Accordingly, if aTFT is formed by using a thus obtained crystalline silicon film, it isexpected that the electrical characteristics and reliability of the TFTis badly affected, which is another problem.

It is confirmed that the catalytic element remaining in the crystallinesemiconductor film is segregated irregularly, especially in a crystalgrain boundary concentratedly, and if this segregation exists in aregion which becomes a component in the semiconductor film (especiallyin a channel formation region and a connection portion between thechannel formation region and a source region or a drain region), it isconsidered that the segregation becomes an escape route (leak path) of aweak current, and causes an abrupt increase in an off current (currentwhen a TFT is in an off state).

Yet another object of the present invention is therefore to provide amethod in which a gettering step for quickly reducing the concentrationof a catalytic element remaining in a crystalline semiconductor filmafter a crystallization step using the catalytic element is also carriedout by a low temperature process.

It becomes possible to improve the throughput of the heating treatmentby using an RTA apparatus as set forth above. Besides, when a lightsource is made to irradiate in a pulsed manner, a treatment temperaturecan be lowered before heat is conducted to glass, so that a heatingtreatment of a semiconductor film formed on a glass substrate becomespossible.

Further, heat transfer by lighting of the light source controlled in apulsed manner is controlled through a temperature sensor, and coolingmeans for preventing transfer of heat exceeding the glass transitiontemperature to the glass substrate is used in accordance with thiscontrol. Since heating and cooling are carried out at the same time, itis possible to prevent the temperature from exceeding the glasstransition temperature during the heating treatment or to shorten a timein which the temperature exceeds it. Besides, by repeating this heatingtreatment, even in a period in which such a temperature that a catalyticelement for facilitating crystallization of a semiconductor film isdiffused in the semiconductor is held, the glass substrate is notdeformed, and the heating treatment of the semiconductor film forcrystallization of the semiconductor film and for gettering of thecatalytic element can be efficiently carried out in a relatively shorttime. This method is called a “Plural Pulse Thermal Annealing”(hereinafter referred to as PPTA) in the present specification.

The PPTA (Plural Pulse Thermal Anneal) apparatus uses a heating methodcapable of performing rapid heating and rapid cooling in which a lightsource is made to emit light in a pulsed manner to irradiate so thatonly a semiconductor film is instantaneously heated and the heating canbe stopped before the heat is conducted to a glass substrate. Thus, theglass substrate is not deformed or damaged by heat. Further, the heattransfer by lighting of the light source controlled in the pulsed manneris controlled with a temperature sensor, and cooling means forpreventing transfer of heat exceeding the glass transition temperatureto the glass substrate is used in accordance with this control. Besides,by repeating this heating treatment, even in a period in which such atemperature that a catalytic element for facilitating crystallization ofthe semiconductor film is diffused in the semiconductor is held, theglass substrate is not deformed, and the heating, treatment of thesemiconductor film for crystallization of the semiconductor film and forgettering, of the catalytic element can be efficiently carried out in arelatively short time.

Incidentally, FIG. 20 shows an example of the PPTA (Plural Pulse ThermalAnneal) apparatus. In FIG. 20, a first heat treatment chamber 751, asecond heat treatment chamber 752, and a third heat treatment chamber753 are connected to the circumference of a first transport chamber 750through gates 772 d to 772 f. The structure of these heat treatmentchambers is the same as that of FIG. 1. A refrigerant is introduced intothe respective heat treatment chambers through flow control means 767from a cylinder 766. Exhausting means for reducing the pressure in theprocess chamber is constructed by turbo molecular pumps 768 a to 768 cand dry pumps 769 a to 769 c. Besides, there are provided circulators771 a to 771 c for circulating the refrigerant and purifiers 770 a to770 c for purifying the refrigerant. Although not shown, turning on andoff of a light source and supply of the refrigerant are controlled by acomputer. In the treatment chambers are equipped light sources 762 a-762c and substrate stages 763 a-763 c, respectively.

The second transport chamber 754 is provided with transport means 760,which transports a substrate to be treated to the first treatmentchamber 750, a surface treatment chamber 755, and a cooling chamber 756.The surface treatment chamber 755 is provided with a spinner 764. Thecooling chamber 756 is provided with a substrate stage 765. In thestructure of a load chamber 757 and an unload chamber 758, the movementof the substrate to be treated is made by transport means 761. Note,reference numeral 759 indicates transport means.

The present invention is a method of fabricating a semiconductor deviceusing the heating treatment apparatus as described above, and ischaracterized by comprising a first step of adding a catalytic elementfor facilitating, crystallization to an amorphous semiconductor filmformed on an insulating surface, and a second step of forming acrystalline semiconductor film by controlling a light source toirradiate a pulsed light to the amorphous semiconductor film tocrystallize it.

Besides, the present invention is a method of fabricating asemiconductor device using the heating treatment apparatus as describedabove, and is characterized by comprising a first step of adding acatalytic element for facilitating crystallization to an amorphoussemiconductor film formed on an insulating surface, and a second step offorming a crystalline semiconductor film by controlling a light sourceto irradiate a pulsed light to the amorphous semiconductor film tocrystallize it, wherein a light emitting time of the light source is 1to 60 seconds.

The above invention is characterized by comprising a step of improvingcrystallinity by irradiating a laser light to the crystallinesemiconductor film after the second step.

The above invention is characterized in that in the second step, theinside of the treatment chamber has a reduced pressure atmosphere.

The above invention is characterized in that in the second step, anatmosphere in the treatment chamber contains oxygen at a concentrationof 5 ppm or less.

Besides, the present invention is a method of fabricating asemiconductor device by using the heating treatment apparatus asdescribed above and is characterized by comprising a first step ofadding an impurity element to a crystalline semiconductor film formed byadding a catalytic element to an amorphous semiconductor film andcarrying out a heating treatment, and a second step of irradiating apulsed light to the crystalline semiconductor film added with theimpurity element by controlling a light source, wherein gettering of thecatalytic element is carried out by the light irradiation treatment.

Besides, the present invention is a method of fabricating asemiconductor device by using the heating treatment apparatus asdescribed above and is characterized by comprising a first step ofadding an impurity element to a crystalline semiconductor film formed byadding a catalytic element to an amorphous semiconductor film andcarrying out a heating treatment, and a second step of gettering thecatalytic element by controlling a light source to irradiate a pulsedlight to the crystalline semiconductor film added with the impurityelement, wherein a light emitting time of the light source is 1 to 40seconds.

The above invention is characterized in that the impurity element is anelement belonging to group 15 of the periodic table.

The above invention is characterized in that the impurity element is anelement belonging to group 15 of the periodic table and an elementbelonging to group 13 of the periodic table.

The above invention is characterized in that the impurity element is anelement belonging to group 18 of the periodic cable, an elementbelonging to group 15 of the periodic table, and an element belonging togroup 13 of the periodic table.

The above invention is characterized in that the concentration of theimpurity element belonging to the group 13 is {fraction (1/100)} to 100times as high as the concentration of the impurity element belonging tothe group 15.

Besides, the present invention is a method of fabricating, asemiconductor device by using the heating treatment apparatus asdescribed above and is characterized by comprising a first step offorming an amorphous semiconductor film on a crystalline semiconductorfilm formed by adding a catalytic element to an amorphous semiconductorfilm and carrying out a heating treatment, and adding an impurityelement to the amorphous semiconductor film, and a second step ofgettering the catalytic element by controlling a light source toirradiate a pulsed light to the crystalline semiconductor film.

The above invention is characterized in that the impurity element is anelement belonging to group 18 of the periodic table.

The above invention is characterized in that the impurity element is anelement belonging to group 18 of the periodic table, an elementbelonging to group 15 of the periodic table, and an element belonging togroup 13 of the periodic table.

The above invention is characterized in that in the second step, theinside of a treatment chamber is exhausted and its pressure is 26.6 Paor less.

The above invention is characterized in that in the second step, anatmosphere in a treatment chamber, especially in the vicinity of thecrystalline semiconductor film contains oxygen at a concentration of 2ppm or less.

The above invention is characterized in that the impurity elementbelonging to the group 15 of the periodic table is an element selectedfrom N, P, As, Sb and Bi.

The above invention is characterized in that the impurity elementbelonging to the group 13 of the periodic table is an element selectedfrom B, Al, Ga, In and Tl.

The above invention is characterized in that the impurity elementbelonging to the group 18 of the periodic table is an element selectedfrom Ar, Kr and Xc.

The above invention is characterized in that in the second step, acontinuous holding time of a temperature exceeding a glass strain pointis 20 seconds or less.

The above invention is characterized in that a holding time of highestintensity of the light source in the second step is 1 to 5 seconds.

The above invention is characterized in that in the second step, coolingusing a nitrogen gas, an inert gas or a liquid as a refrigerant iscarried out simultaneously.

The above invention is characterized in that in the second step, avicinity of the crystalline semiconductor film is in a nitrogen (N₂)atmosphere, an inert gas atmosphere, a hydrogen (H₂) atmosphere, or areducing gas atmosphere.

The above invention is characterized in that the light source is a lightsource for emitting infrared light or ultraviolet light.

The above invention is characterized in that a halogen lamp, a metalhalide lamp, a xenon arc lamp, or a reduced pressure mercury lamp isused as the light source.

The above invention is characterized in that the light source irradiatesan upper side of the substrate, a lower side of the substrate, or thelower side and the upper side of the substrate.

The above invention is characterized in that the catalytic element isone or plural kinds of elements selected from Ni, Fe, Co, Ru, Rh, Pd,Os, Ir, Pt, Cu, and Au.

Besides, the present invention is a method of fabricating asemiconductor device using the heating treatment apparatus as describedabove and is characterized by comprising a first step of forming anamorphous semiconductor film on an insulating surface, a second step ofadding a catalytic element for facilitating crystallization to a surfaceof the amorphous semiconductor film, a third step of forming acrystalline semiconductor film by controlling a light source toirradiate a pulsed light to the amorphous semiconductor film added withthe catalytic element to crystallize the amorphous semiconductor film, afourth step of adding an impurity element to the crystallinesemiconductor film, and a fifth step of gettering the catalytic elementby controlling the light source to irradiate a pulsed light to thecrystalline semiconductor film added with the impurity element.

Besides, the present invention is a method of fabricating asemiconductor device using the heating treatment apparatus as describedabove and is characterized by comprising a first step of forming anamorphous semiconductor film on an insulating surface, a second step offorming a catalytic element inclusion region by coating a catalyticelement for facilitating crystallization onto a surface of the amorphoussemiconductor film, a third step of forming a crystalline semiconductorfilm by controlling a light source to irradiate a pulsed light to theamorphous semiconductor film coated with the catalytic element tocrystallize the amorphous semiconductor film, a fourth step of adding animpurity element to the crystalline semiconductor film, a fifth step ofgettering the catalytic element by controlling the light source toirradiate a pulsed light to the crystalline semiconductor film addedwith the impurity element, a sixth step of transforming the crystallinesemiconductor film in which the catalytic element has keen (lettered inthe fifth step into a semiconductor layer of a desired shape, a seventhstep of forming a gate insulating film covering the semiconductor laser,an eighth step of forming a gate electrode on the gate insulating film,a ninth step of adding an n-type impurity element to the semiconductorlayer, a tenth step of adding a p-type impurity element to thesemiconductor layer which becomes an active layer of a subsequentp-channel TFT, and an eleventh step of activating the impurity elementsadded to the semiconductor layer by controlling the light source toirradiate a pulsed light.

The above invention is characterized in that the crystallizing step ofthe semiconductor layer and the activating step of the impurity elementsadded to the semiconductor layer are carried out in a reduced pressureatmosphere in which an oxygen concentration is reduced by performingexhaustion by a rotary pump and a mechanical booster pump.

The above invention is characterized in that the impurity element addedin the fourth step is an impurity element belonging to group 15 of theperiodic table, and the impurity element belonging to the group 15 ofthe periodic table is an element selected from N, P, As, Sb and Bi.

The above invention is characterized in that the impurity element addedin the fourth step is an impurity element belonging to group 15 of theperiodic table and an element belonging to group 13 of the periodictable, and the impurity element belonging to the group 15 of theperiodic table is an element selected from N, P, As, Sb and Bi, and theelement belonging to the group 13 of the periodic table is an elementselected from B, Al, Ga, In and Tl.

The above invention is characterized in that the third step and thefifth step are carried out under a condition that a vicinity of thecrystalline semiconductor film has a nitrogen (N₂) atmosphere, an inertgas atmosphere, a hydrogen (H₂) atmosphere, or a reducing gasatmosphere.

The above invention is characterized in that the catalytic element isone kind or plural kinds of elements selected from Ni, Fe, Co, Ru, Rh,Pd, Os, Ir, Pt, Cu, and Au.

By carrying out the crystallization treatment of the semiconductor filmand the movement (gettering) treatment of the catalytic element existingin the semiconductor film by using the apparatus as described above, itbecomes possible to shorten a time required for the crystallizing stepof the semiconductor film and a time required for the gettering step ofthe catalytic element added to the semiconductor film.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1F are views for explaining a heating treatment(crystallization, gettering) disclosed in the present invention;

FIGS. 2A and 2B are views for explaining a heating treatment (gettering)disclosed in the present invention;

FIG. 3 is a view showing an example of a heating treatment apparatusused in the present invention;

FIGS. 4A and 4B are a view showing measurement results of intensitychange of a light source and a view showing measurement results oftemperature change of a semiconductor film and a substrate,respectively, of the present invention;

FIGS. 5A and 5B are views showing results of observation of acrystalline semiconductor film fabricated by using the presentinvention;

FIGS. 6A to 6D are views showing fabricating steps of TFTs of Embodiment1;

FIGS. 7A to 7C are views showing fabricating steps of the TFTs ofEmbodiment 1;

FIGS. 8A to 8C are views showing fabricating steps of the TFTs ofEmbodiment 1;

FIG. 9 is a view showing an active matrix substrate fabricated by usingthe present invention;

FIGS. 10A to 10D are views showing fabricating steps of TFTs ofEmbodiment 2;

FIGS. 11A to 11C are views showing fabricating steps of TFTs ofEmbodiment 2;

FIG. 12 is a view showing an active matrix type liquid crystal displaydevice of Embodiment 4;

FIGS. 13A to 13F are views showing examples of electronic instruments ofEmbodiment 8;

FIGS. 14A to 14D are views showing examples of electronic instruments ofEmbodiment 8;

FIGS. 15A to 15C are views showing examples of electronic instruments ofEmbodiment 8;

FIG. 16 is a view showing a light-emitting device of Embodiment 7;

FIGS. 17A to 17E are views showing fabricating steps of TFTs ofEmbodiment 5;

FIGS. 18A to 18C are views showing fabricating steps of TFTs ofEmbodiment 5;

FIGS. 19A to 19D are views showing fabricating steps of TFTs ofEmbodiment 6;

FIG. 20 is a view showing an example of a heating treatment apparatusused in the present invention; and

FIG. 21 is a view of showing fabricating steps of TFTs of Embodiment 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment Mode 1

A crystallization method and a gettering method using a PPTA apparatusdisclosed in the present invention will be described with reference toFIGS. 1A to 1F.

First, an under insulating film 11 is formed on an insulating surface ofa glass substrate 10 transparent to light. As the under insulating film,any one of a silicon oxide film, a silicon nitride film, and a siliconnitride oxide film may be used, or these films may be laminated.

Next, an amorphous semiconductor film 12 is formed on the underinsulating film 11. In Embodiment Mode 1, an amorphous silicon film wasformed to a thickness of 55 nm. Subsequently, as a catalytic element forfacilitating, crystallization, nickel (Ni) is coated onto the surface ofthe amorphous silicon film 12 by a well-known method, and a catalyticelement containing layer 13 is formed.

This substrate is moved to a treatment chamber 14, and a heatingtreatment is carried out. As the heating treatment, eleven halogen lamps(infrared light) located at the lower side of the substrate and tenhalogen lamps at the upper side are switched on for 1 to 60 seconds(preferably 30 to 60 seconds) and 1 to 10 times (preferably 2 to 6times). FIG. 4A shows the intensity of the light source during theheating treatment, a solid line graph of FIG. 4B shows temperature inthe vicinity of the substrate measured by a thermocouple (508 b of FIG.3) of the PPTA apparatus embedded in a silicon wafer, and a dotted linegraph of FIG. 4B shows temperature measured by a radiation thermometer(508 a of FIG. 3) at the outside of the treatment chamber from the rearside of the center portion of the substrate. From these graphs, it isconceivable that heat (measured by the thermocouple embedded in thesilicon wafer) supplied by the halogen lamp is 700 to 1300° C. InEmbodiment Mode 1, although the halogen lamp is used as the lightsource, it is also preferable to use an ultraviolet lamp, such as axenon lamp, as the light source.

Incidentally, as shown in FIG. 3, the PPTA apparatus disclosed in thepresent specification is provided with, as cooling means, means forcaroling the inside of a reaction chamber and the reaction chamber.Here, the light source is controlled in a pulsed manner to irradiate thesemiconductor film and to hear-treat the semiconductor film, and at thesame time, cooling is performed by using a refrigerant so that the glasssubstrate is not distorted. As the refrigerant for cooling the inside ofthe reaction chamber, an inert gas such as a nitrogen gas or a heliumgas may he used, and as the refrigerant for cooling the reaction chamberitself, an inert gas such as a nitrogen gas or a helium gas, or a liquidor both may he used. In Embodiment Mode 1, the nitrogen gas of 2 to 10(slm) is made to flow in.

As the lamp used as the light source, as long as the temperature can becontrolled in a pulsed manner as shown by the graph of FIG. 4B, not onlythe infrared light, but also a lamp emitting ultraviolet light, or anyone of a general metal halide lamp, a xenon arc lamp, and a reducedpressure mercury lamp may be used.

Further, the heating treatment for crystallization is further effectiveif exhaustion is performed by using a rotary pump, a mechanical boosterpump and the like and the heat treatment is carried out in a reducedpressure atmosphere in which an oxygen concentration is reduced. It isappropriate that the pressure in the treatment chamber is made 1.33×10⁴Pa or less. Alternatively, it may be 26.7 Pa to 1.33×10⁴ Pa. Further, itmay be 13.3 Pa or less.

FIG. 5A shows a state in which a crystalline silicon film 16, which isobtained through crystallization by the PPTA apparatus, is observed byan optical microscope. FIG. 5B shows the result of an observation, madeby a SEM, of a grain boundary of a semiconductor film treated bysecoetching. In FIG. 5A, the observation is made in a transmission modeof the optical microscope, and from the difference betweentransmissivity of crystalline silicon and that of amorphous silicon, itis conceivable that a black portion is a region of amorphous silicon.There are few regions which seem to be amorphous silicon as it is. Here,in order to observe the state of crystallization, an image processingwas further carried out and a crystallization rate was measured.

A photograph taken after the observation by the optical microscope ismade to have two gradations by the image processing. Since amorphoussilicon and crystalline silicon can be separated in green, thephotograph was made a green image, and this image was made to have twogradations to be divided into an amorphous silicon region and acrystalline silicon region, and then a calculation was made using imageprocessing software (NIH-Image). According to this measurement method,the crystallization rate was 99.8%.

Next, a gettering treatment using the PPTA apparatus is ill be describedwith reference to FIGS. 1D and 1E and FIG. 2. A mask insulating film 17is formed in order to add an impurity element (typically phosphorus)belonging to the group 15 of the periodic table and having a getteringfunction to a crystalline silicon film 16, and phosphorus (P) is addedto form a gettering region 18. In this gettering region 18, phosphorusof 1×10²⁰ to 1×10²¹ atoms/cm³ is added. Incidentally, as the impurityelement belonging to the group 15 of the periodic table, an elementselected from N, P, As, Sb and Bi maw be used.

The catalytic element is coated on the whole surface of thesemiconductor film, and the catalytic element of 1×10¹⁷ to 1×10¹⁹atoms/cm³ remains even in a region which becomes a subsequent channelformation region. A lamp light is transformed into a pulse state and isirradiated to the lower surface and the upper surface of the substrate(hereinafter, a lamp light which is transformed into a pulse state andis irradiated is referred to as a pulsed light) to cause the betteringregion 18 to getter the catalytic element. Similarly to the heatingtreatment for crystallization, a halogen lamp is used for the pulsedlight, heating up to 1220° C. is performed, and the temperature is heldfor 40 seconds. Next, cooling is performed down to 300 to 400° C.Although the effect of gettering, can be confirmed by only one suchtreatment, the treatment is preferably performed 2 to 20 times. By thisheating treatment, the catalytic element in the semiconductor film canbe reduced to 1×10¹⁷ atoms/cm³ or less. During the heating treatment, inorder to prevent heat from being conducted to the glass substrate, thenitrogen gas of 2 to 10 (slm) as the refrigerant is made to flow intothe reaction chamber. Incidentally, similarly to the heating treatmentfor crystallization, if the heating, treatment for gettering is alsocarried out in a reduced pressure atmosphere lower than the atmosphericpressure by performing exhaustion by the rotary pump and the mechanicalbooster pump, the efficiency of gettering is further improved.

In the above heating treatment, although the lamp light is irradiated tothe semiconductor film in the pulsed manner to carry out the treatmentsuch as crystallization or gettering, if heating is performed like apulse (for example, the light source itself is moved or the substrateitself is moved to produce the same effect as that obtained byirradiating the semiconductor film with the pulsed light), it is notnecessary to control the light source (lamp) in the pulsed manner.

Here, an example of the PPTA apparatus used in the present inventionwill be described in brief with reference to FIG. 3. The apparatus is asingle wafer processing type and a treatment chamber 500 is formed ofquartz. A water-cooled cooling device 501 for cooling is provided aroundthe treatment chamber 500. As light sources 502, rod-like halogen lampsare provided at the lower side and the upper side of a substrate, andthe light sources at both sides are used in Embodiment Mode 1. However,the light sources may be used only at a single side, and the user maysuitably choose a structure. The light sources 502 are controlled by alight source control device 503 and emits a pulsed light (including, forexample, a wavelength of 0.5 μm to 3 μm).

A nitrogen gas as a refrigerant (gas) 520 is supplied to the treatmentchamber 500 from a refrigerant supply source 504 through a flow controldevice 505. Incidentally, on the basis of results measured bytemperature sensors 508 a and 508 b connected to a temperature detector507, control means 506 controls the supply amount of the refrigerant andthe intensity of the light source. The refrigerant supplied to thetreatment chamber 500 is exhausted to the outside from an exhaustionport 509, and the treatment chamber 500 is always filled with a cleangas.

A substrate 514 is set on a substrate holder in a loader/unloaderchamber 513, and is transported to the treatment chamber 500 bytransport means 511 of a transport chamber 512. A partition valve 510 isprovided between the transport chamber 512 and the treatment chamber500. The treatment chamber 500 is exhausted by a rotary pump 515 and amechanical booster pump 516.

Embodiment Mode 2

In the crystallization step of an amorphous semiconductor set forth inEmbodiment Mode 1, the heating treatment for crystallization of anamorphous semiconductor film may be carried out in a vacuum atmosphereof 0.1 Pa or lower. In this case, a pump capable of realizing a highvacuum, such as a turbo molecular pump, is used to highly evacuate theinside of the treatment chamber, and then, the light source iscontrolled to carry out the heating treatment.

Embodiment Mode 3

In Embodiment Mode 3, an example different from the gettering methodusing the PPTA apparatus of Embodiment Mode 1 will be described.Incidentally, since a different point is an impurity element added to agettering region, FIGS. 1A-1F are used for the description.

In accordance with Embodiment Mode 1, an under insulating film 11 isformed on an insulating surface of a glass substrate 10 transparent tolight. Next, an amorphous semiconductor film 12 is formed on the underinsulating film 11. In Embodiment Mode 3, an amorphous silicon film wasformed to a thickness of 55 nm (FIG. 1A).

Subsequently, nickel (Ni) as a catalytic element for facilitatingcrystallization is coated onto the surface of the amorphous silicon film12 by a well-known method to form a catalytic element containing layer13, and then, the amorphous silicon film 12 is crystallized by a heatingtreatment in a treatment chamber 14 to form a crystalline silicon film16. Laser light may be irradiated to the crystalline silicon film 16after this heating treatment to improve the crystallinity, (FIGS. 1B and1C).

The concentration of the catalytic element remaining in the crystallinesilicon film 16 formed in the manner described above is thus reduced. Agettering treatment using the PPTA apparatus will be described withreference to FIGS. 1D and 1E and FIGS. 2A-2B. Note, FIG. 2B shows asectional view of FIG. 2A with a cut line A-A′. A mask insulating film17 is formed to add an impurity clement (typically phosphorus) belongingto the group 15 of the periodic table and having a gettering functionand an impurity element belonging to the group 13 to the crystallinesilicon film 16, and phosphorus (P) and boron (B) are added to form agettering region 18. In this gettering region 18, the concentration ofthe impurity element belongings to the group 13 is {fraction (1/100)} to100 times as high as the concentration of the impurity element belongingto the group 15 (in Embodiment Mode 3, phosphorus of 1×10¹⁹ to 1×10²¹atoms/cm³ and boron of 1×10¹⁹ to 1×10²¹ atoms/cm³ are added). A vaporphase method such as an ion doping method or a plasma doping method, ora method of forming a layer containing the element belonging to thegroup 13 and/or group 15 by a solid phase method or a liquid phasemethod using a solution is used as the adding method. Incidentally, asthe impurity element belonging to the group 15 of the periodic table, anelement selected from N, P, As, Sb and Bi may be used, and as theelement belonging to the group 13 of the periodic table, an elementselected from B, Al, Ga, In and Tl may be used.

This substrate is again moved to the treatment chamber 14 and theheating treatment is carried out. As the heating treatment, elevenhalogen lamps (infrared light) located at the lower side of thesubstrate and ten halogen lamps at the upper side are switched on for 1to 180 seconds (preferably 30 to 60 seconds) and 1 to 30 times(preferably 2 to 10 times). The treatment is carried out at such atemperature that the glass substrate is not largely distorted or warped.In Embodiment Mode 3, on the basis of measurement from the rear surfaceof the substrate by a radiation thermometer, control is made so that thesubstrate temperature at this time becomes 700° C. or lower, andcontinuous holding of the temperature above 667° C. as the glass strainpoint is suppressed within 20 seconds. In Embodiment Mode 3, althoughthe halogen lamp is used as the light source, it is also preferable touse an ultraviolet lamp, such as a xenon lamp, as the light source.

Incidentally, as shown in FIG. 3, the PPTA apparatus disclosed in thepresent specification is provided with, as cooling means, means forcooling the inside of the reaction chamber and the reaction chamber, andthe light source is controlled in the pulsed manner to irradiate thesemiconductor film and to heat-treat the semiconductor film, and at thesame time, cooling is performed by using the refrigerant so that theglass substrate is not distorted. As the refrigerant in the reactionchamber, an inert gas such as a nitrogen gas or a helium gas may beused, and as the refrigerant for cooling the reaction chamber itself, aninert gas such as a nitrogen gas or a helium gas, or a liquid, or bothmay be used. In Embodiment Mode 3, the nitrogen gas of 2 to 10 (slm) ismade to flow in.

As the lamp used as the light source, as long as the illumination can becontrolled in the pulsed manner, not only the infrared light, but also alamp emitting ultraviolet light, or any one of a general metal halidelamp, a xenon arc lamp, a carbon arc lamp, and a reduced pressuremercury lamp may be used.

Further, the gettering effect is improved by carrying out the heatingtreatment in a reduced pressure atmosphere lower than the atmosphericpressure by performing exhaustion by the rotary pump and the mechanicalbooster pump. In Embodiment Mode 3, nitrogen having high purity(concentration of CH₄, CO, CO₂, H₂, H₂O and O₂ contained in nitrogen is1 ppb or less) is made to flow at a rate of 5 l/min to hold the pressureat 26.7 Pa or less, and a nitrogen atmosphere of an oxygen concentrationof 5 ppm or less (in Embodiment Mode 3, 2 ppm or less) is formed. Theheating treatment step at 450 to 950° C. for 4 to 24 hours is carriedour in this nitrogen atmosphere. Incidentally, in Embodiment Mode 3,although the nitrogen atmosphere is used, if the oxygen concentrationcan be made 5 ppm or less, the atmosphere may contain a gas notcontaining oxygen, for example, an inert gas such as helium (He), neon(Ne), or argon (Ar). Besides, a gas which is not deposited bydecomposition due to heat or does not react with the semiconductor film,for example, hydrogen (H₂) may be used.

The catalytic element is coated on the whole surface of thesemiconductor film 21, and the catalytic element of 1×10¹⁷ to 1×10¹⁹atoms/cm³ remains even in a region which subsequently becomes a channelformation region. The lamp light is transformed into a pulse state andis irradiated to the lower surface and the upper surface of thesubstrate (hereinafter, a lamp light which is transformed into the pulsestate and is irradiated is referred to as a pulsed light 20), and thegettering region 18 is made to getter the catalytic element. The halogenlamp is used for the pulsed light 20, and lamp heating up to 700° C. isperformed and immediately after that, cooling is performed down to 600°C. (preferably 450° C. or lower). Although the effect of gettering canbe confirmed even when this treatment is performed only once, thetreatment is preferably performed 2 to 30 times.

By this heating treatment, as shown in FIG. 1F and FIGS. 2A-2B, nickelin the crystalline silicon film is moved in the direction of an arrow atthis heating treatment step, and is trapped by the gettering functioninto the gettering region 18. That is, nickel is removed from thecrystalline silicon film, and the concentration of nickel contained inthe crystalline silicon film can be reduced to 1×10¹⁷ atoms/cm³ or less,preferably to 1×10¹⁶ atoms/cm³ or less. During the heating treatment, inorder to prevent heat from being conducted to the glass substrate, anitrogen gas of 2 to 10 (slm) as the refrigerant is made to flow intothe reaction chamber.

In the above-described heating treatment, although the semiconductorfilm is irradiated with the lamp light in the pulsed manner and thetreatment such as crystallization or gettering is carried out, ifheating is performed like a pulse (for example, the light source itselfis moved or the substrate itself is moved to produce the same effect asthat obtained by irradiating the semiconductor film with the pulsedlight), it is not necessary to control the light source (lamp) in thepulsed manner. The crystalline silicon film thus obtained is patternedto form a region 22 to be an active layer of a TFT later.

Embodiment Mode 4

In Embodiment Mode 4, an example different from the gettering methodusing, the PPTA apparatus of Embodiment Mode 3 using FIGS. 1A-1F will bedescribed.

In accordance with Embodiment Mode 1, a crystalline semiconductor filmis formed by using a catalytic element. Note that, the crystallinity maybe improved by irradiating a laser light to the crystallinesemiconductor film (crystalline silicon film) obtained by the heatingtreatment.

In the crystalline silicon film formed in the manner described above,the catalytic element for facilitating crystallization is used, and thecatalytic element is removed after crystallization by the getteringfunction of phosphorus, and a more excellent crystalline silicon filmcan be obtained by reducing the concentration of the catalytic elementremaining in the crystalline silicon film.

Here, the gettering treatment using the PPTA apparatus will bedescribed. A mask film 17 is formed to add an impurity element(typically phosphorus) belonging to the group 15 of the periodic tableand having the gettering function, an impurity element (typically boron)belonging to the group 13 of the periodic table, and an impurity element(typically argon) belonging to the group 18 of the periodic table to acrystalline silicon film 16, and phosphorus (P) and argon (Ar) are addedto form a gettering region 18. At this time, although the getteringregion 18 may be formed by adding phosphorus (P) and boron (B), in thiscase, the concentration of the impurity element belonging to the group13 in this gettering region 18 is {fraction (1/100)} or more to 100 orless times as high as the concentration of the impurity elementbelonging to the group 15 (in Embodiment Mode 4, phosphorus of 1×10¹⁹ to1×10²¹ atoms/cm³ and boron of 1×10¹⁹ to 1×10²¹ atoms/cm³ are added). Avapor phase method such as an ion doping method or a plasma dopingmethod, or a method of forming a layer containing an element belongingto the group 13 and/or group 15 by a solid phase method or a liquidphase method using a solution is used as the adding method. Argon (Ar)may be mixed into a film when a semiconductor film is deposited bysputtering. Further, as the gettering method, an amorphous semiconductorfilm may be formed so as to be adjacent to a region to be gettered.

Note that, as the impurity element belonging to the group 18 of theperiodic table, Kr, Xe or the like may be used in addition to Ar.

Further, after the catalytic element is added and the crystallinesilicon film 16 is formed by heating as shown in FIGS. 1C and 1D, then,as shown in FIG. 21, an amorphous silicon film containing an impurityelement belonging to the group 18 of the periodic table is formed on thecrystalline silicon film 16 and a heating treatment is performed, sothat this amorphous silicon film functions as a gettering region, andthe catalytic element remaining in the crystalline silicon film 16 canbe moved. Note that, since the amorphous silicon film 31 functioning asthe gettering region is removed by etching or the like after thegettering step, it is appropriate that the amorphous silicon film 31 isformed after a barrier layer 30 for protecting the crystalline siliconfilm against an etchant at the etching treatment is formed on thecrystalline silicon film 16. Note that, a chemical oxide film fanned bya treatment with ozone water or a chemical oxide film formed by atreatment with a solution of a mixture of sulfuric acid, hydrochloricacid, nitric acid, or the like and hydrogen peroxide water may be usedas this barrier layer 30. These films can be removed by a hydrofluoricacid treatment.

This substrate is again moved into the treatment chamber 14 and aheating treatment is carried out. As the heating treatment, elevenhalogen lamps (infrared light) 15 installed at the lower side of thesubstrate and ten halogen lamps at the upper side thereof are switchedon for 1 to 180 seconds (preferably 30 to 60 seconds) and 1 to 30 times(preferably 2 to 10 times). The treatment is carried out at such atemperature that the glass substrate is not largely distorted or warped.In Embodiment Mode 4, on the basis of measurement from the rear surfaceof the substrate by the radiation thermometer, control is made so thatthe substrate temperature at this time becomes 700° C. or lower, andcontinuous holding of a temperature not smaller than 667° C. as theglass strain point is suppressed within 20 seconds. Besides, in order toimprove a throughput and to reduce electric power consumption, lightirradiation may be carried out for several minutes to hold a temperatureof 600 to 700° C. In Embodiment Mode 4, although the halogen lamp isused as the light source, it is also preferable to use an ultravioletlamp, such as a xenon lamp, as the light source.

Note that, as shown in FIG. 3, the PPTA apparatus disclosed in thepresent specification is provided with, as cooling means, means forcooling the inside of the reaction chamber and the reaction chamber.Here, the light source is controlled in the pulsed manner to irradiatethe semiconductor film and to subject the semiconductor film to the heattreatment, and at the same time, cooling is performed by using therefrigerant so that the glass substrate is not distorted. As therefrigerant in the reaction chamber, an inert gas such as a nitrogen gasor a helium gas may be used, and as the refrigerant for cooling thereaction chamber itself, an inert gas such as a nitrogen gas or a heliumgas, or a liquid, or both may be used. In Embodiment Mode 4, thenitrogen gas of 2 to 10 (slm) is made to flow in.

As the lamp used as the light source, as long as the illumination can becontrolled abruptly in the pulsed manner, not only the infrared light,but also a lamp emitting ultraviolet light, or any one of a generalhalogen lamp, a metal halide lamp, a xenon arc lamp, a carbon arc lamp,and a reduced pressure mercury lamp may be used.

Further, in the treatment chamber 14, exhaustion is performed by usingthe rotary pump and the mechanical booster pump, and the heatingtreatment is carried out in the reduced pressure atmosphere lower thanthe atmospheric pressure so that the gettering effect is improved. InEmbodiment Mode 4, nitrogen having high purity (concentration of CH₄,CO, CO₂, H₂, H₂O and O₂ contained in nitrogen is 1 ppb or less) is madeto flow at a rate of 5 l/min to hold a pressure of 26.7 Pa or less, andthe nitrogen atmosphere of an oxygen concentration of 5 ppm or less (inEmbodiment Mode 4, 2 ppm or less) is formed. In this nitrogenatmosphere, the heating treatment step at 450° C. to 950° C. for 4 to 24hours is carried out. Note that, in Embodiment Mode 4, although thenitrogen atmosphere is used, if the oxygen concentration can be made 5ppm or less, the atmosphere may contain a gas not containing oxygen, forexample, an inert gas such as helium (He), neon (Ne), or argon (Ar).Besides, a gas which is not deposited by decomposition due to heat ordoes not react with the semiconductor film, for example, hydrogen (H₂)may be used.

The catalytic element is applied onto the whole surface of thesemiconductor film, and the catalytic element of 1×10¹⁷ to 1×10¹⁹atoms/cm³ remains even in a region which becomes a subsequent channelformation region. The lamp light is transformed into the pulse state andis irradiated from the lower surface and the upper surface of thesubstrate (hereinafter, the lamp light which is transformed into thepulse state and is irradiated is referred to as a pulsed light), and thegettering region 18 is made to getter the catalytic element. The halogenlamp is used as the pulsed light, and lamp is heated up to 700° C. andimmediately after that, is cooled down to 600° C. (preferably 450° C. orlower). Although the effect of gettering can be confirmed even when thistreatment is carried out only once, the treatment is preferably carriedout 2 to 30 times. Besides, for the purpose of improving throughput andreducing electric power consumption, optical irradiation may be carriedout for several minutes to hold a temperature of 600° C. to 700° C.

By this heating treatment, as shown in FIG. 1F, nickel in thecrystalline silicon film is moved in the direction of an arrow at thisheating treatment step, and is trapped by the gettering function ofphosphorus into the gettering region 18. That is, nickel is removed fromthe crystalline silicon film, and the concentration of nickel containedin the crystalline silicon film can be reduced to 1×10¹⁷ atoms/cm³ orless, preferably to 1×10¹⁶ atoms/cm³ or less. During the heatingtreatment, in order to prevent heat from being conducted to the glasssubstrate, the nitrogen gas of 2 to 10 (slm) as the refrigerant is madeto flow into the reaction chamber.

In the above-described heating treatment, although the semiconductorfilm is irradiated with the lamp light in the pulsed manner and thetreatment such as crystallization or gettering is carried out, ifheating is performed like a pulse (for example, the light source itselfis moved or the substrate itself is moved to produce the same effect asthat obtained by irradiating the semiconductor film with the pulsedlight), it is not necessary to control the light source (lamp) in thepulsed manner.

Embodiment 1

An example of a method of fabricating a TFT substrate using the presentinvention will be described in Embodiment 1 with reference to FIGS. 6Ato 9.

First, in Embodiment 1, a glass substrate made of aluminoborosilicateglass, barium borosilicate glass, or the like transparent to light, or a(lass substrate having a specific gravity of 2.5 g/cm³ or less and athermal expansion coefficient of 35.0×10⁻⁷/° C. or less is used. Anunderlying insulating film 101 is formed on the glass substrate 100. Asthe underlying insulating film 101, SiH₄ and N₂O are used in a CVDapparatus to form a silicon nitride oxide (SiNO) film 101 a, and next, asilicon oxide nitride (SiON) film 101 b is formed in the same chamber.The films are formed so that the film thickness of the laminate of theSiNO film and the SiON film becomes 50 to 200 nm.

Next, an amorphous silicon film 102 is formed as an amorphoussemiconductor film. Next, a mask insulating film (not shown) is formedon the amorphous silicon film 102. The mask insulating film is used in astep in which an impurity element for imparting a p type (hereinafterreferred to as a p-type impurity element) is added to the amorphoussilicon film 102 through the mask insulating film. As the p-typeimpurity element, representatively an element belonging to the group 13,typically boron or gallium can be used. This step (called a channeldoping step) is a step for controlling the threshold voltage of a TFT.Note that, here, boron is added by an ion doping method in whichdiborane (B₂H₆) is plasma excited without performing mass separation. Ofcourse, an ion implantation method in which mass separation is performedmay be used.

Next, a crystallization treatment of the amorphous silicon film 102 iscarried out. First, a nickel acetate salt solution containing nickel of10 ppm in terms of weight is applied onto the surface of the amorphoussilicon film 102 to form a catalytic element containing layer 103 (FIG.6A). A well-known method such as coating by a spinner or a sputteringmethod may be used as the coating method. Subsequently, as shown by thesolid line graph of FIG. 4B, a light source is controlled to performpulsed irradiation for heating (hereinafter, a light irradiated in apulsed manner by controlling a light source is referred to as a pulsedlight), an operation in which 1220° C. (measured by the temperaturesensor indicated by 508 b of FIG. 3) is held for 40 seconds and thepulsed light is cut for 5 seconds is made one cycle, and this isrepeated three times, and at the fourth pulse, 1220° C. (measured by thetemperature sensor indicated by 508 b of FIG. 3) is held for 60 seconds.Note that, a time period in which the pulsed light 104 holds the highestintensity is about 1 to 5 seconds. In Embodiment 1, although the pulsedlight 104 is irradiated four times, the irradiation may be performed 2to 10 times. By this, a crystalline silicon film 105 is formed. Notethat, in order to further raise the crystallization rate and to repairdefects in crystal grains, laser irradiation may be performed on thecrystalline silicon film 105 (FIG. 6B).

Besides, before the crystallization treatment, a heat treatment forreducing the hydrogen content of the amorphous silicon film may becarried out.

Subsequently, in order to getter the catalytic element used for thecrystallization treatment from the crystalline silicon film 105, animpurity element (typically phosphorus) belonging to the group 15 of theperiodic table and having the gettering function is added to form agettering region 107. A mask insulating film 170 is formed andphosphorus is added to a region where the crystalline silicon film isexposed. Not only phosphorus but also boron may be added into thegettering region 107. Thereafter, a pulsed light 106 is irradiated. Asthe irradiated pulsed light, a pulsed light is suitable in which heatingis performed at a rate of 100 to 200° C./second up to 1220° C., and thetemperature is held for 40 seconds and is reduced at a rate of 50 to150° C./sec down to 300 to 400° C. Besides, in order to. prevent theglass substrate from being heated to the glass transition temperature orhigher, the nitrogen gas of 2 to 10 (slm) as the refrigerant is made toflow in. By irradiating such a pulsed light once, the catalytic elementis gettered by the gettering region 107. In order to obtain a sufficientgettering, effect, the pulsed light irradiation may be carried out 2 to20 times. Besides, it is preferable that the step of the heatingtreatment for crystallization of the semiconductor film and forgettering of the catalytic element is carried out in a reduced pressureatmosphere in which an oxygen concentration is reduced by the exhaustperformed by a rotary pump and a mechanical booster pump (FIG. 6C).

The excellent crystalline silicon film 105 obtained in this way ispatterned into island shape to form semiconductor layers 108 to 112which subsequently become active layers of TFTs (FIG. 6D). Next, a gateinsulating film 113 having a thickness of 50 to 150 nm is formed by aplasma CVD method on the island-like, semiconductor layers 108 to 112.Next, as a conductive film for formation of gate electrodes, aconductive film (A) 114 having a thickness of 20 to 100 nm and aconductive film (B) 115 having a thickness of 100 to 400 nm are formed.In Embodiment 1, although the conductive film (A) 114 is formed of TaN,and the conductive film (B) 115 is formed of W, the film may be formedof an element selected from Ta, W, Ti, Mo, Al and Cu, or an alloymaterial or a compound material containing the element as its mainingredient (FIG. 7A).

Next, masks 116 a to 116 g made of resist are formed, and the conductivefilm (A) 114 and the conductive film (B) 115 are etched, so that gateelectrodes 117 to 120 made of the laminate of the conductive film (A)and the conductive film (B) are formed. Although the etching method isnot limited, it is appropriate that an ICP (inductively coupled plasma)etching method is used. CF₄ and Cl₂ are used as the etching gas. Acapacitance wiring line 121 which becomes an upper electrode of astorage capacitor, and wiring lines 122 and 123 are formed in the samestep.

After the gate electrodes 117 to 120 and the wiring lines 121 to 123 areformed, an impurity element for imparting an n type (hereinafterreferred to as an n-type impurity element) is added to the semiconductorlayers 108 to 112 through the gate insulating film 113 by an ion dopingmethod white using the gate electrodes as masks. By this step, n-typeimpurity regions 124 a to 124 e each having an impurity concentration of1×10¹⁶ to 1×10¹⁸ atoms/cm³ are formed (FIG. 7B).

Next, a second etching treatment is carried out while the masks made ofresist remain as they are, so that gate electrodes having second shapesand wirings lines 125 to 131 are formed. Subsequently, while the gateelectrodes having the second shapes and the wiring lines 125 to 131 areused as masks, an n-type impurity element is further added. By this,n-type impurity regions (n+) each subsequently becoming a source regionor a drain region and having an n-type impurity element concentration of1×10²⁰ to 1×10²¹ atoms/cm³, and n-type impurity regions (n−) 132 a to132 e each subsequently becoming a low concentration impurity region(hereinafter referred to as an LDD region) provided closer to a channelformation region than the n-type impurity region (n+) and having ann-type impurity element concentration of 1×10¹⁸ to 1×10¹⁹ atoms/cm³ areformed (FIG. 7C).

Then, masks 133 and 134 made of resist are formed in regions whichbecome subsequent N-channel TFTs, and a p-type impurity element is addedto form p-type impurity regions 135 a and 135 b. Note that, it isappropriate that the impurity concentration of the p-type impurityregion 135 is made to become 1.5 to 3 times as high as the maximum valueof the concentration of the n-type impurity added in the former step,that is, 2×10²⁰ to 2×10²¹ atoms/cm³ (FIG. 3A).

Next, an N-channel TFT 201 and a second P-channel TFT 203 of asubsequent driving circuit 206 are covered with masks 136 and 137 madeof resist and an etching treatment is carried out, so that gateelectrodes of third shapes and wiring lines 138 to 142 are formed in afirst P-channel TFT 202 of the subsequent driving circuit 206, a pixelTFT 204 and wiring lines.

Next, a heating treatment for activating the impurity elements added tothe semiconductor film is carried out. In this heating treatment, thePPTA apparatus shown in FIG. 3 is used, and the pulsed light isirradiated several times to carry out the activation. The pulsed lightis irradiated from the rear surface side of the substrate (in thepresent specification, a surface on which a TFT is formed is made asubstrate surface). By this heating treatment, the impurity elements canbe certainly activated. Note, although in Embodiment 1 the pulsed laserlight is irradiated from only the rear surface side of the substrate,the pulsed light can be irradiated from both of the front and rear sidesof the substrate.

After the activation treatment, a first interlayer insulating film 143made of a silicon nitride film or a silicon nitride oxide film is formedby a plasma CVD method. Then, a heating treatment for releasing hydrogenfrom the first interlayer insulating film 143 and hydrogenating thesemiconductor film is carried out. This heating treatment may be carriedout at 350 to 450° C. (preferably 410° C.) in a clean oven.Alternatively, a well-known hydrogenating treatment in an atmospherecontaining hydrogen generated from formation of plasma may be carriedout (FIG. 8C).

Next, as a second interlayer insulating film 144, an organic insulatingmaterial such as acrylic or polyimide is used to perform flattening.Then, contact holes reaching the semiconductor films 108 to 112 whichbecome active layers of subsequent TFTs are formed in the firstinterlayer insulating film 143 and the second interlayer insulating film144. A Ti film having a thickness of 100 to 200 nm, an alloy film (alloyfilm of Al and Ti) having a thickness of 250 to 350 nm, and a Ti filmhaving a thickness of 50 to 150 nm are laminated thereon, and arepatterned into desired shapes, so that connection wiring lines 145 co152 are formed to electrically connect the respective TFTs.

Besides, in a pixel portion 207, a pixel electrode 153 is formed. Thepixel electrode 153 is electrically connected to a drain region 124 d ofthe pixel TFT 204 and a lower electrode (impurity doped semiconductorfilm) 135 c of a storage capacitor 205.

An N-channel TFF 201 includes a channel formation region 161, the sourceregion and drain region 124 a, and the LDD region 132 a in the activelayer.

A first P-channel TFT 202 includes a channel formation region 162, thesource region and drain region 135 in the active layer.

A second P-channel TFT 203 includes a channel formation region 163, thesource region and drain region 135 b, and the LDD region 135 e in theactive layer. Note that, the gate electrode 127 includes a regionoverlapping with the LDD region 135 e.

A pixel TFT 204 includes a channel formation region 164, the sourceregion and drain region 124 d, and the LDD region 132 d in the activelayer.

The storage capacitor 204 includes the lower electrode (semiconductorfilm doped with the impurity element) 112, a dielectric (an insulating,film formed continuously from the gate insulating film 113) and an upperelectrode (made of the laminate of the conductive film (A) and theconductive film (B) forming the gate electrodes) 129.

At this point, an active matrix substrate made of the driving circuit206 including the CMOS structure 208 formed of the N-channel TFF 201 andthe P-channel TFT 202, and the pixel portion 207 including the pixel TFT204 and the storage capacitor 205 is fabricated.

When the present invention as described in Embodiment 1 is used, theheating treatment can be carried out by the PPFA apparatus in a shorttime, the throughput is improved, and the highly reliable TFT can beefficiently fabricated.

Embodiment 2

The crystallization step and the gettering step of the present inventioncan also be applied to a bottom gate type TFT substrate. A descriptionthereof will be given with reference to FIGS. 10A to 10D and FIGS. 11Ato 11C.

An insulating film (not shown) such as a silicon oxide film, a siliconnitride film, or a silicon nitride oxide film is formed on a substrate50, and a conductive film is formed to form a gate electrode, and ispatterned into a desired shape to obtain a gate electrode 51 As theconductive film, an element selected from Ta, Ti, W, Mo, Cr and Al maybe used, or a conductive film containing one of these elements as itsmain ingredient may be used (FIG. 10A).

Next, a gate insulating film 52 is formed. The gate insulating film maybe a single layer of a silicon oxide film, a silicon nitride film, or asilicon nitride oxide film, or may have a laminate structure of somefilms.

Next, as an amorphous semiconductor film, an amorphous silicon film 53having a thickness of 10 to 1150 nm is formed by a thermal CVD method, aplasma CVD method, a reduced pressure CVD method, an evaporation method,or a sputtering method. Note that, since the gate insulating film 52 andthe amorphous silicon film 53 can be formed by the same film growthmethod, both may be continuously formed. The continuous formationprevents the films from being once exposed to the air, so that pollutionof the surface can be prevented, ant fluctuation of characteristics of afabricated TFT and variation of threshold voltage can be reduced (FIG.10B).

Next, a crystallization treatment of the amorphous silicon film iscarried out. A catalytic element is added to the amorphous silicon filmto form a catalytic element containing layer 54. Subsequently, a lightsource (pulsed light 55) controlled in a pulsed manner is used toirradiate the amorphous silicon film, so that a crystallinesemiconductor film (crystalline silicon film) 56 is formed.

Subsequently, a gettering treatment of the catalytic element for movingthe catalytic element from a region which becomes a semiconductor layerof a TFT is carried out. A mask 57 is formed on the crystallinesemiconductor film 56, and an impurity element having a getteringfunction is added to a selected region of the semiconductor film to forma gettering region 58. As the impurity element to be added, it isappropriate that an impurity element belonging to the group 15 of theperiodic table, or an impurity element belonging to the group 15 of theperiodic table and an impurity element belonging to the group 13 of theperiodic table, or an table and an impurity element belonging to thegroup 15 of the periodic table, an impurity it element belonging to thegroup 13 of the periodic table and an impurity element belonging to thegroup 18 of the periodic table may be added. Thereafter, a source(pulsed light 59) controlled in the pulsed manner is used to move thecatalytic element into the gettering region 58 (FIG. 10D).

Next, a protection insulating film 60 is formed to a thickness of 100 to400 nm. Subsequently, a mask (not shown) made of resist is used to addan impurity element for imparting an n type to a crystalline siliconfilm which becomes an active layer of a subsequent N-channel TFT 70, andto add a p-type impurity element to a crystalline silicon film whichbecomes an active layer of a subsequent P-channel TFT 71, so that asource region, a drain region and an LDD region are formed (FIG. 11A).

Next, a treatment for activating the impurity elements added to thecrystalline silicon film is carried out. As the activation treatment,the heating treatment using the pulsed light disclosed in EmbodimentModes and Embodiment 1 may be used. Subsequently, after the activationtreatment, a well-known hydrogenating treatment in an atmospherecontaining hydrogen generated by formation of plasma may be carried out.

Next, the insulating film 60 on the crystalline silicon film is removed,and after the crystalline silicon film is formed into a semiconductorlayer of a desired shape, an interlayer insulating film 61 is formed.The interlayer insulating film is formed of an insulating filmcontaining silicon, such as a silicon oxide film, a silicon nitridefilm, or a silicon nitride oxide film, or a laminate of those to have athickness of 500 to 150 nm (FIG. 1B).

Thereafter, contact holes reaching source regions or drain regions 74 ofrespective TFTs are formed, and wiring lines 62 for electricallyconnecting the respective TFTs are formed (FIG. 11C). Note, referencenumeral 72 indicates an LDD region; 73 and 75, channel formationregions.

As described above, the present invention can be applied irrespective ofthe shape of the TFT.

Embodiment 3

In the TFT fabricating process described in Embodiment 1, acrystallization step of an amorphous semiconductor film may be carriedout as described below.

First, a nickel acetate salt solution containing nickel of 100 ppm interms of weight is applied onto the surface of an amorphous silicon film102, and a catalytic element containing layer 103 is formed. The coatingmethod may be a well-known method such as coating by a spinner or asputtering method. Subsequently, evacuation is performed by a rotarypump and a mechanical booster pump, and nitrogen of high purity(concentration of CH₄, CO, CO₂, H₂, H₂O and O₂ contained in nitrogen is1 ppb or less) is made to flow at 2 l/min to hold a pressure of 26.7 Pa,so that a nitrogen atmosphere is formed. In this nitrogen atmosphere,heating at 1220° C. for 60 seconds was performed only once. Note that, atime period in which the pulsed light holds the maximum intensity isabout 1 to 5 seconds. By this, a crystalline silicon film 105 is formed.Note that, in order to further raise the crystallization ratio and torepair defects in crystal grains, laser irradiation may he carried outto the crystalline silicon film 105.

Besides, a heat treatment for reducing the hydrogen content of theamorphous silicon film may be carried out before the crystallizationtreatment.

Embodiment 4

In Embodiment 4, a description will be given of a process of fabricatingall active matrix driving liquid crystal display device from a TFTsubstrate fabricated by the application of Embodiments 1 to 3. FIG. 12shows a state in which a TFT substrate is bonded to a counter substrate180 by a sealing member. A columnar spacer 183 is formed on the TFTsubstrate. It is appropriate that the columnar spacer 183 is formed toconform with a cavity of a contact portion formed over a pixelelectrode. The columnar spacer 183 is formed to have a height of 3 to 10μm although depending on a liquid crystal material used. Since a recessportion corresponding to a contact hole is formed at the contactportion, the spacer is formed to conform with this portion so thatdisturbance of orientation of liquid crystal can be prevented.Thereafter, an orientation film 182 is formed and a rubbing treatment iscarried out. A transparent conductive film 184, and an orientation film181 are formed on the counter substrate 180. Thereafter, the TFTsubstrate is bonded to the counter substrate 180 by the sealing member,and liquid crystal is injected to form a liquid crystal layer 185. Inthe manner described above, the active matrix driving liquid crystaldisplay device can be completed.

Embodiment 5

Another method of fabricating an active matrix substrate by using thePPTA apparatus will be described with reference to FIGS. 17A to 18C.Note that, FIGS. 17A to 17E and FIGS. 18A to 18C illustrate a method offorming a pixel TFT 320 and a storage capacitor 321 of a pixel portion.

An underlying insulating film 301 is formed on a surface of a substrate300. As the underlying insulating film 301, a silicon oxide film, asilicon nitride film, or a silicon nitride oxide film, or a laminatestructure of some films may be used. In Embodiment 5, a silicon nitrideoxide film having a thickness of 50 to 200 nm is formed by a plasma CVDmethod using SiH₄ and N₂O.

Next, a considerably thin film (hereinafter referred to as a thin filmfor convenience) 302 of Ni is formed. The substrate 300 on which theunderlying insulating film 301 is formed is put in a film growth chamberof a parallel flat plate type plasma CVD apparatus using an electrodemade of a material containing Ni or a positive column type plasma CVDapparatus, and plasma is generated in an atmosphere of nitrogen,hydrogen, or inert gas. In Embodiment 5, by a plasma treatment under theconditions of substrate temperature of 300° C., pressure of 6.65 Pa,argon of 100 (sccm), and RF electric power of 50 W, the Ni thin film 302of a Ni amount of 1×10¹⁰ atoms/cm² to 1×10¹³ atoms/cm² is formed. The Nithin film 302 functions as the catalytic element for facilitatingcrystallization in a subsequent step of crystallizing a semiconductorlayer (FIG. 17A). Note that, in Embodiment 5, although the Ni thin filmis formed, as long a, an element (called a catalytic element in thepresent specification) has a function of facilitating crystallization ofa semiconductor film, in addition to nickel (Ni), a thin film containingone kind or plural kinds of elements selected from Fe, Co, Ru, Rh, Pd,Os, Ir, Pt, Cu, and Au may be formed.

Next, an amorphous silicon film is formed on the Ni thin film 302. Thefilm is patterned into a desired shape to form a semiconductor layer 304which becomes an active layer of a subsequent TFT, and a semiconductorlayer 305 which becomes a lower electrode of a subsequent storagecapacitor (FIG. 17B).

Subsequently, a mask insulating film 306 is formed on the semiconductorlayers 304 and 305. As the mask insulating film, a silicon oxide film isformed by a plasma CVD method. Thereafter, a p-type impurity element(typically boron or gallium) is added to the semiconductor layer throughthe mask insulating film 306. This step (called a channel doping step)is carried out to control the threshold voltage of a TFT. By this step,the p-type impurity element (in Embodiment 5, boron) at a concentrationof 1×10¹⁵ to 1×10¹⁸ atoms/cm³ is added to the semiconductor layer (FIG.17C).

Next, the mask insulating film 306 is removed, and a (gate insulatingfilm 307 is formed (FIG. 17D). The gate insulating film is formed byusing a plasma CVD method or a sputtering method. Subsequently, in orderto form a gate electrode; a conductive film (A) 308 and a conductivefilm (B) 309 are formed. In Embodiment 5, the conductive film (A) ismade of tantalum nitride (TaN), and this film is formed to a thicknessof 50 to 100 nm. The conductive film (B) is formed to a thickness of 100to 300 nm by using a high melting metal such as tungsten (W) ormolybdenum (Mo). The conductive film (A) and the conductive film (B) areetched to form a gate electrode 310 and a capacitance wiring line 311which becomes an upper electrode of a subsequent storage capacitor.Although the etching method is not limited, the ICP (inductively coupledplasma) etching, method is preferably used. At this time, a mixture gasof CF₄ and Cl₂ is used as the etching gas.

An n-type impurity element is added to the semiconductor layer while thegate electrode and the capacitance wiring line are used as masks, sothat an n-type impurity region 312 which contains the n-type impurityelement at a concentration of 1×10²⁰ to 1×10²¹ atoms/cm³ and becomes asource reunion or a drain region of an active layer of a subsequent TFT,an n-type impurity region 313 which contains the n-type impurity elementat a concentration of 1×10¹⁸ to 1×10¹⁹ atoms/cm³ and becomes an LDDregion of the active layer of the subsequent TFT, and a channelformation region 314 are formed (FIG. 17E).

Next, a region which becomes a subsequent N-channel TFT is covered witha mask, and a p-type impurity element is added to a region which becomesa subsequent P-channel TFT (not shown). Note that, in this step, thep-type impurity region doped with the p-type impurity element at aconcentration of 2×10²⁰ to 2×10²¹ atoms/cm³ is formed (not shown). Note,reference numerals 315 and 316 indicate impurity regions formed in thesemiconductor layer 305 of the lower electrode of the storage capacitor321. Reference numeral 317 denotes a region not added with the impurityelements.

Subsequently, while cooling with a refrigerant is performed by the PPTAapparatus, a step of crystallizing the semiconductor layer in theamorphous state is carried out. A light source 318 is controlled in apulsed manner to irradiate the substrate. The light source is controlledso that the temperature becomes 800 to 1100° C. when measured by athermocouple (508 b of FIG. 3) embedded in a silicon wafer, thistemperature is held for 1 to 30 seconds, and such irradiation ispreferably performed 1 to 5 times. Since the gate insulating film 307and the ate electrodes 310 and 311 are formed on the semiconductorlayer, heat becomes hard to dissipate from the semiconductor layer, andthe semiconductor layer can be efficiently crystallized in a short time.Note that, in this step, it is preferable that exhaustion is performedby a rotary pump and a mechanical booster pump to reduce an oxygenconcentration in an atmosphere, and the heating treatment is carried outin the atmosphere which contains nitrogen or inert gas and has a reducedpressure of about 0.001 to 26.7 Pa in the treatment chamber (FIG. 18A).

Next, a first interlayer insulating film 319 is formed on the gateelectrode. As the first interlayer insulating film, it is appropriatethat an insulating film containing silicon, such as a silicon nitridefilm, a silicon oxide film, or a silicon nitride oxide film, or alaminate film of a combination of those is formed to a thickness ofabout 100 to 400 nm (FIG. 18B).

Subsequently, the PPTA apparatus is used and the light source controlledin the pulsed manner performs irradiation several times, so that theimpurity elements added to the semiconductor layer are activated. Inthis step, the Ni element which functions as the catalytic element atthe time of crystallization and subsequently diffuses in thesemiconductor layer is moved (arrows of FIG. 18C) toward the region 312where the impurity element (phosphorus) having the gettering function isadded at a high concentration, so that the concentration of thecatalytic element (Ni) of a region which becomes the channel formationreunion 314 of the subsequent active layer can be reduced to aconcentration of 1×10¹⁷ atoms/cm³ or less (preferably 1×10¹⁶ atoms/cm³or less). Besides, in this step, it is preferable that exhaustion isperformed by a rotary pump and a mechanical booster pump to reduce anoxygen content in an atmosphere and the heating treatment is carried outin the reduced pressure atmosphere.

Hereinafter, if fabrication is performed in accordance with the stepssubsequent to the hydrogenating treatment of Embodiment 1, thesemiconductor device can be efficiently fabricated in a short timewithout using an electric furnace.

Embodiment 6

Another method of fabricating an active matrix type substrate having apixel TFT 410 and a storage capacitor 411 thereon using the PPTAapparatus will he described with reference to FIGS. 19A to 19D.

In Embodiment 6, steps up to a step of forming a conductive film (A) 308and a conductive film (B) 309 may be carried out in accordance withEmbodiment 5. Note that, the same reference characters are used in thesame steps.

After the conductive film (A) 308 and the conductive film (B) 309 areformed, crystallization of a semiconductor layer in an amorphous stateis carried out in the PPTA apparatus by cooling with a refrigerant andby irradiation from a light source controlled in a pulsed manner (FIG.19A). The light source is controlled so that a temperature of 800 to1100° C. measured by a thermocouple (508 b of FIG. 3) e,embedded in asilicon wafer is held for 1 to 30 seconds, and this irradiation isrepeated 1 to 5 times.

As described in Embodiment 6, when crystallization is carried out in astate where a gate insulating film and a gate electrode are formed onthe semiconductor layer, heat becomes hard to dissipate, andcrystallization of the semiconductor layer can be more efficientlycarried out in a short time. Note that, in this step, it is preferablethat exhaustion is performed by a rotary pump and a mechanical boosterpump to reduce an oxygen content in an atmosphere and the heatingtreatment is carried out in the reduced pressure atmosphere.

Next, the conductive film (A) 308 and the conductive film (B) 309 arepatterned into desired shapes to form a gate electrode 401 and acapacitance wiring line 402 which becomes an upper electrode of asubsequent storage capacitor. Although a method of forming the gateelectrode and the storage capacitor is not limited, similarly toEmbodiment 1, it is appropriate that the IPC etching method is used.

An n-type impurity element and a p-type impurity element are added inaccordance with the step of Embodiment 5 to form impurity regions 403,404, 406 and 407, and regions 405 and 408 not added with the impurityelements (FIG. 19B). Subsequently, a first interlayer insulating film409 is formed by forming an insulating film containing silicon, such asa silicon nitride film, a silicon oxide film, or a silicon nitride oxidefilm, or a laminate film of a combination of those to have a thicknessof about 100 to 400 nm (FIG. 19C).

Next, a heating treatment for activating the impurity elements by thePPTA apparatus is carried out. In the step of the heating treatment foractivation, the catalytic element in the semiconductor layer can begettered by the region 403 doped with phosphorus at a high concentration(FIG. 19D).

In accordance with Embodiment 6, a semiconductor device including asemiconductor layer with excellent crystallinity can be efficientlyfabricated without using an electric furnace. Embodiment 6 is combinedwith Embodiment 3 so that the active matrix type liquid crystal displaydevice can be completed.

Embodiment 7

In Embodiment 7, a process of fabricating an active matrix drivinglight-emitting device using a TFT substrate (active matrix substrate)obtained according to Embodiment 1 will be described with reference toFIG. 16.

A glass substrate is used as a substrate 1601. On the glass substrate1601, an N-channel TFT 1652 and a P-channel TFT 1653 are formed in adriving circuit 1650, and a switching TFT 1654 and a current controllingTFT 1655 are formed in a pixel portion 1651. These TFTs are formed byusing semiconductor layers 1603 to 1606, a second insulating film 1607as a gate insulating film, gate electrodes 1608 to 1611, and the like.

A first insulating film 1602 formed on the substrate 1601 is provided byforming a silicon nitride oxide (expressed by SiO,N,) film, a siliconnitride film or the like to have a thickness of 50 to 200 nm. Aninterlayer insulating film is made of an inorganic insulating film 1618formed of silicon nitride, silicon nitride oxide or the like and anorganic insulating film 1619 formed of acrylic, polyimide or the like.

Although a circuit structure of the driving circuit 1650 is differentbetween a gate signal side driving circuit and a data signal sidedriving circuit, the explanation thereof is omitted here. Wiring lines1612 and 1613 are connected to the N-channel TFT 1652 and the P-channelTFT 1653, and a shift register, a latch circuit, a buffer circuit andthe like are formed by using these TFTs.

In the pixel portion 1651, a data wiring line 1614 is connected to asource side of the switching TFT 1654, and a wiring line 1615 at a drainside is connected to the gate electrode 1611 of the current controllingTFT 1655. Besides, a source sidle of the current controlling TFT 1655 isconnected to a power Supply line 1617, and an electrode 1616 at a drainside is connected to an anode of an EL element.

The EL element including an anode, a cathode, and a layer (hereinafterreferred to as an EL layer) in which electroluminescence is obtained andwhich contains an organic compound is formed over the TFT of the pixelportion. Note that, luminescence of an organic compound includes lightemission (fluorescence) obtained when a singlet excited state isreturned to a ground state, and light emission (phosphorescence)obtained when a triplet excited state is returned to the ground state,and both are included.

The EL element is provided after banks 1620 and 1621 are formed using anorganic resin such as acrylic or polyimide, preferably a photosensitiveorganic resin so as to cover the wiring line. In Embodiment 7, the ELelement 1656 includes an anode 1622 formed of ITO (indium tin oxide), anEL layer 1623, and a cathode 1624 formed by using a material such as analkaline metal or an alkaline-earth metal, for example, MgAg or LiF. Thebanks 1620 and 1621 are formed so as to cover an end of the anode 1622,and are provided to prevent the cathode and the anode fromshort-circuiting at this portion.

The cathode 1624 of the EL element is provided on the EL layer 1623. Asthe cathode 1624, a material including magnesium (Mg), lithium (Li) orcalcium (Ca) having a low work function is used. Preferably, anelectrode formed of MEAL (mixed material of Mg and Ag at a ratio of 10to 1) may be used. In addition, a MgAgAl electrode, a LiAl electrode ora LiFAI electrode can be enumerated.

Although it is necessary that the laminate made of the EL layer 1623 andthe cathode 1624 is separately formed for every pixel, since the ELlayer is extremely weak against water, a normal photolithographytechnique can not be used. Besides, the cathode 1624 fabricated by usingalkaline metal is easily oxidized. Accordingly, it is preferable that aphysical mask member such as a metal mask is used to selectively formthem by a vapor phase method such as a vacuum evaporation method, asputtering method, or a plasma CVD method. Besides, a protectionelectrode for protection against outside moisture or the like may bestacked on the cathode 1624. It is preferable that a low resistancematerial including aluminum (Al), copper (Cu) or silver (Ag) is used forthe protection electrode.

In order to obtain high brightness with low electric power consumption,an organic compound (hereinafter referred to as a triplet compound)emitting light by a triplet exciton (triplet) is used as the materialforming the EL layer. Note that, a singlet compound indicates a compoundemitting light through only singlet excitation, and the triplet compoundindicates a compound emitting light through triplet excitation.

As the triplet compound, organic compounds disclosed in the followingpapers can be cited as typical materials. (1) T. Tsutsui. C. Adachi, S.Saito, Photochemical Processes in Organized Molecular Systems, ed. K.Honda, (Elsevier Sci. Pub., Tokyo, 1991) p. 437. (2) M. A. Baldo, D. F.O'Brien, Y. You, A. Shoustikov, S. Sibley, M. E. Thompson, S. R.Forrest, Nature 395 (1988) p. 151. (3) M. A. Bakdo, S. Lamansky, P. E.Burrows, M. F. Thompson, S. R. Forrest, Appl. Phys. Lett., 75 (1999) p.4(4) T. Tsutsui, M. -J. Yang, M. Yahiro, K. Nakamura, T. Watanabe, T.Tsuji, Y. Fukuda, T. Wakimoto, S. Mayaguchi, Jpn. Appl. Phys., 38 (12B)(1999) L1502.

The triplet compound has higher light emission efficiency than thesinglet compound, and an operation voltage (voltage required to cause anEL element to emit light) can be lowered to obtain the same luminousbrightness.

In FIG. 16, the switching TFT 1654 is made to have a multi-gatestructure, and the current controlling TFT 1655 is provided with an LDDoverlapping with the gate electrode. A TFT using polycrystalline siliconhas a high operation speed, so that deterioration of hot carrierinjection or the like is apt to occur. Thus, as shown in FIG. 16, toform the TFTs (the switching TFT having a sufficiently low off currentand the current controlling TFT resistant to the hot carrier injection)having different structures according to the functions in a pixel isvery effective in fabrication of a display device which has highreliability and enables excellent image display (high operationperformance). In the manner described above, an active matrix drivinglight emitting device can be completed.

Embodiment 8

The CMOS circuit and the pixel portion formed by implementing thepresent invention can be used inactive matrix type liquid crystaldisplay. That is, the present invention can be implemented in all ofelectronic apparatus integrated with the liquid crystal display deviceat display portions thereof.

As such electronic apparatus, there are pointed out a video camera, adigital camera, a projector (rear type or front type), a head mountdisplay (goggle type display), a personal computer, a portableinformation terminal (mobile computer, portable telephone or electronicbook) and the like. Examples of these are shown in FIGS. 13A-13F,14A-14D and 15A-15C.

FIG. 13A shows a personal computer including a main body 2001, an imageinput portion 2002, a display portion 2003 and a keyboard 2004.

FIG. 13B shows a video camera including a main body 2101, a displayportion 2102, a voice input portion 2103, operation switches 2104, abattery 2105 and an image receiving portion 2106.

FIG. 13C shows a mobile computer including a main body 2201, a cameraportion 2202, an image receiving portion 2203, an operation switch 2204and a display portion 2205.

FIG. 13D shows a goggle type display including a main body 2301, adisplay portion 2302 and an arm portion 2303.

FIG. 13E shows a player using a record medium recorded with programs(hereinafter, referred to as record medium) including a main body 2401,a display portion 2402, a speaker portion 2403, a record medium 2404 andan operation switch 2405. The player uses DVD (digital Versatile Disc)or CD as the record medium and can enjoy music, enjoy movie and carryout game or Internet.

FIG. 13F shows a digital camera including a main both 2501, a displayportion 2502, an eye contact portion 2503, operation switches 2504 andan image receiving portion (not illustrated).

FIG. 14A shows a front type projector including a projection apparatus2601 and a screen 2602.

FIG. 14B shows a rear type projector including a main body 2701, aprojection apparatus 2702, a mirror 2703 and a screen 2704.

Further, FIG. 14C is a view showing an example of a structure of theprojection apparatus 2601 and 2702 in FIG. 14A and FIG. 14B. Theprojection apparatus 2601 or 2702 is constituted by a light sourceoptical system 2801, mirrors 2802, 2804-2806, a dichroic mirror 2803, aprism 2807, a liquid crystal display apparatus 2808, a phase differenceplate 2809 and a projection optical system 2810. The projection opticalsystem 2810 is constituted by an optical system including a projectionlens. Although the embodiment shows an example of three plates type, theembodiment is not particularly limited thereto but may be of, forexample, a single plate type. Further, person of executing theembodiment may pertinently provide an optical system such as an opticallens, a film having a polarization function, a film for adjusting aphase difference or an IR film in an optical path shown by arrow marksin FIG. 14C.

Further, FIG. 14D is a view showing an example of a structure of thelight source optical system 2801 in FIG. 14C. According to theembodiment, the light source optical system 2801 is constituted by areflector 2811, a light source 2812, lens arrays 2813 and 2814, apolarization conversion element 2815 and a focusing lens 2816. Further,the light source optical system shown in FIG. 14D is only an example andthe embodiment is not particularly limited thereto. For example, aperson of executing the embodiment may pertinently provide an opticalsystem such as an optical lens, a film having a polarization function, afilm for adjusting, a phase difference or an IR film in the light sourceoptical system

However, according to the projectors shown in FIG. 14, there is shown acase of using a transmission type liquid crystal display device and anexample of applying a reflection type liquid crystal display device isnot illustrated.

FIG. 15A shows a portable telephone including a display panel 3001, anoperation panel 3002. The display panel 3001 and the operation panel3002 is connected to each other in the connecting portion 3003. In theconnecting panel 3003, the angle θ of a face which is provided thedisplay portion 3004 of the display panel 3001 and a face which isprovided the operation key 3006 of the operation panel 3002 can bechanged arbitrary. Further, a voice output portion 3005, an operationkey 3006, a power source switch 3007 and a sound input portion 3008 arealso included.

FIG. 15B shows a portable book (electronic book) including a main body3001, display portions 3002 and 3003, a record medium 3004, an operationswitch 3005 and an antenna 3006.

FIG. 15C shows a display including a main body 3101, a support base 3102and a display portion 3103. The display according to the invention isadvantageous particularly in the case of large screen formation and isadvantageous in the display having a diagonal length of 10 inch or more(particularly, 30 inch or more).

As has been described, the range of applying the invention is extremelywide and is applicable to electronic apparatus of all the fields. Theelectronic apparatus of the present invention can be implemented byfreely combined with Embodiment Modes and Embodiments 1 to 6.

By using the present invention, even if an electric furnace having highelectric power consumption is not used, a plurality of TFT substratescan be efficiently manufactured from a large glass substrate. Anexcellent crystalline semiconductor film having a large crystal graindiameter can be obtained by the heating treatment with the PPTAapparatus after a catalytic element is added. Further, the catalyticelement remaining in the obtained crystalline semiconductor film can begettered by the PPTA apparatus.

Besides, since the excellent crystalline semiconductor film fabricatedby using the PPTA apparatus as described above can be used for an activelayer of a TFT, the TFT having high reliability and a semiconductordevice using the TFT can be obtained.

What is claimed is:
 1. A method of manufacturing a semiconductor device,said method comprising the steps of: forming an amorphous semiconductorfilm on an insulating surface; adding a catalytic element being capableof promoting crystallization to the amorphous semiconductor film;crystallizing the amorphous semiconductor film by controlling a lightsource to irradiate with a pulsed light to the amorphous semiconductorfilm to form a crystalline semiconductor film.
 2. A method according toclaim 1, further comprising: irradiating with a laser light to thecrystalline semiconductor film to improve crystallinity thereof afterthe crystallizing step.
 3. A method according to claim 1, wherein thecrystallizing step is performed in a reduced pressure atmosphere in atreatment chamber.
 4. A method according to claim 1, wherein thecrystallizing step is performed in an atmosphere comprising oxygen at aconcentration of in a range of 5 ppm or less in a treatment chamber. 5.A method according to claim 1, wherein a continuous holding time of atemperature exceeding a glass strain point is 20 seconds or less in thecrystallizing step.
 6. A method according to claim 1, wherein a holdingtime of highest intensity of the light source is 1 to 5 seconds in thecrystallizing step.
 7. A method according to claim 1, wherein coolingusing at least one selected from the group consisting of a nitrogen gas,an inert gas and a liquid as a refrigerant is carried out simultaneouslyin the crystallizing step.
 8. A method according to claim 1, wherein avicinity of the crystalline semiconductor film is in at least oneselected from the group consisting of a nitrogen (N₂) atmosphere, aninert gas atmosphere, a hydrogen (H₂) atmosphere and a reducing gasatmosphere in the crystallizing step.
 9. A method according to claim 1,wherein the light source is a light source for emitting at least oneselected from the group consisting of an infrared light and anultraviolet light.
 10. A method according to claim 1, wherein at leastone selected from the group consisting of a halogen lamp, a metal halidelamp, a xenon arc lamp and a reduced pressure mercury lamp is used asthe light source.
 11. A method according to claim 1, wherein the lightsource irradiates a front side of the substrate, a rear side of thesubstrate, or the rear side and the front side of the substrate.
 12. Amethod according to claim 1, wherein the catalytic element comprises atleast one selected from the group consisting of Ni, Fe, Co, Ru, Rh, Pd,Os, Ir, Pt, Cu and Au.
 13. A method according to claim 1, wherein thesemiconductor device is one selected from the group consisting of avideo camera, a digital camera, a front type projector, a rear typeprojector, a head mount display (goggle type display), a personalcomputer, a portable information terminal such as a mobile computer, aportable telephone or an electronic book.
 14. A method of manufacturinga semiconductor device, said method comprising the steps of: forming anamorphous semiconductor film on an insulating surface; adding acatalytic element being capable of promoting crystallization to theamorphous semiconductor film; crystallizing the amorphous semiconductorfilm by controlling a light source to irradiate with a pulsed light tothe amorphous semiconductor film to form a crystalline semiconductorfilm, wherein a light emitting time of the light source is in a range of1 to 60 seconds.
 15. A method according to claim 14, further comprising:irradiating with a laser light to the crystalline semiconductor film toimprove crystallinity thereof after the crystallizing step.
 16. A methodaccording to claim 14, wherein the crystallizing step is performed in areduced pressure atmosphere in a treatment chamber.
 17. A methodaccording to claim 14, wherein the crystallizing step is performed in anatmosphere comprising oxygen at a concentration of in a range of 5 ppmor less in a treatment chamber.
 18. A method according to claim 14,wherein a continuous holding time of a temperature exceeding a glassstrain point is 20 seconds or less in the crystallizing step.
 19. Amethod according to claim 14, wherein a holding time of highestintensity of the light source is 1 to 5 seconds in the crystallizingstep.
 20. A method according to claim 14, wherein cooling using at leastone selected from the group consisting of a nitrogen gas, an inert gasand a liquid as a refrigerant is carried out simultaneously in thecrystallizing step.
 21. A method according to claim 14, wherein avicinity of the crystalline semiconductor film is in at least oneselected from the group consisting of a nitrogen (N₂) atmosphere, aninert gas atmosphere, a hydrogen (H₂) atmosphere and a reducing gasatmosphere in the crystallizing step.
 22. A method according to claim14, wherein the light source is a light source for emitting at least oneselected from the group consisting of an infrared light and anultraviolet light.
 23. A method according to claim 14, wherein at leastone selected from the group consisting of a halogen lamp, a metal halidelamp, a xenon arc lamp and a reduced pressure mercury lamp is used asthe light source.
 24. A method according to claim 14, wherein the lightsource irradiates a front side of the substrate, a rear side of thesubstrate, or the rear side and the front side of the substrate.
 25. Amethod according to claim 14, wherein the catalytic element comprises atleast one selected from the group consisting of Ni, Fe, Co, Ru, Rh, Pd,Os, Ir, Pt, Cu and Au.
 26. A method according to claim 14, wherein thesemiconductor device is one selected from the group consisting of avideo camera, a digital camera, a front type projector, a rear typeprojector, a head mount display (goggle type display), a personalcomputer, a portable information terminal such as a mobile computer, aportable telephone or an electronic book.
 27. A method of fabricating asemiconductor device, said method comprising the step of: adding acatalytic element to an amorphous semiconductor film; heating theamorphous semiconductor film to form a crystalline semiconductor film;adding an impurity element to the crystalline semiconductor film;irradiating with a pulsed light to the crystalline semiconductor film bycontrolling a tight source, wherein the catalytic element is gettered byirradiating with the pulsed light.
 28. A method according to claim 27,wherein an inside of a treatment chamber is exhausted, and a pressure inthe treatment chamber is 26.6 Pa or less in the irradiating step.
 29. Amethod according to claim 27, wherein an atmosphere in a treatmentchamber comprises oxygen at a concentration of 2 ppm or less.
 30. Amethod according to claim 27, wherein a continuous holding time of atemperature exceeding a glass strain point is 20 seconds or less in theirradiating step.
 31. A method according to claim 27, wherein a holdingtime of highest intensity of the light source is 1 to 5 seconds in theirradiating step.
 32. A method according to claim 27, wherein coolingusing at least one selected from the group consisting of a nitrogen gas,an inert gas and a liquid as a refrigerant is carried out simultaneouslyin the irradiating step.
 33. A method according to claim 27, wherein avicinity of the crystalline semiconductor film is in at least oneselected from the group consisting of a nitrogen (N₂) atmosphere, aninert gas atmosphere, a hydrogen (H₂) atmosphere and a reducing gasatmosphere in the irradiating step.
 34. A method according to claim 27,wherein the light source is a light source for emitting at least oneselected from the group consisting of an infrared light and anultraviolet light.
 35. A method according to claim 27, wherein at leastone selected from the group consisting of a halogen lamp, a metal halidelamp, a xenon arc lamp and a reduced pressure mercury lamp is used asthe light source.
 36. A method according to claim 27, wherein the lightsource irradiates a front side of the substrate, a rear side of thesubstrate, or the rear side and the front side of the substrate.
 37. Amethod according to claim 27, wherein the catalytic element comprises atleast one selected from the group consisting of Ni, Fe, Co, Ru, Rh, Pd,Os, Ir, Pt, Cu and Au.
 38. A method according to claim 27, wherein thesemiconductor device is one selected from the group consisting of avideo camera, a digital camera, a front type projector, a rear typeprojector, a head mount display (goggle type display), a personalcomputer, a portable information terminal such as a mobile computer, aportable telephone or an electronic book.
 39. A method according toclaim 27, wherein the impurity element comprises at least an elementselected from group 15 of the periodic table.
 40. A method according toclaim 39, wherein the element is selected from N, P, As, Sb and Bi. 41.A method according to claim 27, wherein the impurity element comprisesat least a first element selected from group 15 of the periodic tableand at least a second element selected from group 13 of the periodictable.
 42. A method according to claim 41, wherein a concentration ofthe second element is {fraction (1/100)} to 100 times as high as aconcentration of the second element.
 43. A method according to claim 41,wherein the second element is selected from B, Al, Ga, In and Tl.
 44. Amethod according to claim 41, wherein the first element is selected fromN, P, As, Sb and Bi.
 45. A method according to claim 27, wherein theimpurity element comprises at least a first element selected from group15 of the periodic table, at least a second element selected from group13 of the periodic table and at least a third element selected fromgroup 18 of the periodic table.
 46. A method according to claim 45,wherein the third element is selected from Ar, Kr and Xe.
 47. A methodaccording to claim 45, wherein a concentration of the second element is{fraction (1/100)} to 100 times as high as a concentration of the secondelement.
 48. A method according to claim 45, wherein the first elementis selected from N, P, As, Sb and Bi.
 49. A method according to claim45, wherein the second element is selected from B, Al, Ga, In and Tl.50. A method of fabricating a semiconductor device, said methodcomprising the step of: adding a catalytic element to an amorphoussemiconductor film; heating the amorphous semiconductor film to form acrystalline semiconductor film; adding an impurity element to thecrystalline semiconductor film; irradiating with a pulsed light to thecrystalline semiconductor film by controlling a tight source, whereinthe catalytic element is gettered by irradiating with the pulsed light,wherein a light emitting time of the light source is in a range of 1 to40 seconds.
 51. A method according to claim 50, wherein an inside of atreatment chamber is exhausted, and a pressure in the treatment chamberis 26.6 Pa or less in the irradiating step.
 52. A method according toclaim 50, wherein an atmosphere in a treatment chamber comprises oxygenat a concentration of 2 ppm or less.
 53. A method according to claim 50,wherein a continuous holding time of a temperature exceeding a glassstrain point is 20 seconds or less in the irradiating step.
 54. A methodaccording to claim 50, wherein a holding time of highest intensity ofthe light source is 1 to 5 seconds in the irradiating step.
 55. A methodaccording to claim 50, wherein cooling using at least one selected fromthe group consisting of a nitrogen gas, an inert gas and a liquid as arefrigerant is carried out simultaneously in the irradiating step.
 56. Amethod according to claim 50, wherein a vicinity of the crystallinesemiconductor film is in at least one selected from the group consistingof a nitrogen (N₂) atmosphere, an inert gas atmosphere, a hydrogen (H₂)atmosphere and a reducing gas atmosphere in the irradiating step.
 57. Amethod according to claim 50, wherein the light source is a tight sourcefor emitting at least one selected from the group consisting of aninfrared light and an ultraviolet light.
 58. A method according to claim50, wherein at least one selected from the group consisting of a halogenlamp, a metal halide lamp, a xenon arc lamp and a reduced pressuremercury lamp is used as the light source.
 59. A method according toclaim 50, wherein the light source irradiates a front side of thesubstrate, a rear side of the substrate, or the rear side and the frontside of the substrate.
 60. A method according to claim 50, wherein thecatalytic element comprises at least one selected from the groupconsisting of Ni, Fe, Co, Ru, Rh, Pd, Os, Ir, Pt, Cu and Au.
 61. Amethod according to claim 50, wherein the semiconductor device is oneselected from the group consisting of a video camera, a digital camera,a front type projector, a rear type projector, a head mount display(goggle type display), a personal computer, a portable informationterminal such as a mobile computer, a portable telephone or anelectronic book.
 62. A method according to claim 50, wherein theimpurity element comprises at least an element selected from group 15 ofthe periodic table.
 63. A method according to claim 62, wherein theelement is selected from N, P, As, Sb and Bi.
 64. A method according toclaim 50, wherein the impurity element comprises at least a firstelement selected from group 15 of the periodic table and at least asecond element selected from group 13 of the periodic table.
 65. Amethod according to claim 64, wherein a concentration of the secondelement is {fraction (1/100)} to 100 times as high as a concentration ofthe second element.
 66. A method according to claim 64, wherein thefirst element is selected from N, P, As, Sb and Bi.
 67. A methodaccording to claim 64, wherein the second element is selected from B,Al, Ga, In and Tl.
 68. A method according to claim 50, wherein theimpurity element comprises at least a first element selected from group15 of the periodic table, at least a second element selected from group13 of the periodic table and at least a third element selected fromgroup 18 of the periodic table.
 69. A method according to claim 68,wherein a concentration of the second element is {fraction (1/100)} to100 times as high as a concentration of the second element.
 70. A methodaccording to claim 68, wherein the first element is selected from N, P,As, Sb and Bi.
 71. A method according to claim 68, wherein the secondelement is selected from B, Al, Ga, In and Tl.
 72. A method according toclaim 68, wherein the third element is selected from Ar, Kr and Xe. 73.A method of fabricating a semiconductor device, said method comprisingthe steps of: adding a catalytic element to a first amorphoussemiconductor film; heating the first amorphous semiconductor film toform a crystalline semiconductor film; forming a second amorphoussemiconductor film on the crystalline semiconductor film; adding animpurity element to the second amorphous semiconductor film; getteringthe catalytic element to the second amorphous semiconductor film bycontrolling a light source to irradiate a pulsed light to thecrystalline semiconductor film.
 74. A method according to claim 73,wherein an inside of a treatment chamber is exhausted, and a pressure inthe treatment chamber is 26.6 Pa or less in the gettering step.
 75. Amethod according to claim 73, wherein an atmosphere in a treatmentchamber comprises oxygen at a concentration of 2 ppm or less.
 76. Amethod according to claim 73, wherein a continuous holding time of atemperature exceeding a glass strain point is 20 seconds or less in thegettering step.
 77. A method according to claim 73, wherein a holdingtime of highest intensity of the light source is 1 to 5 seconds in thegettering step.
 78. A method according to claim 73, wherein coolingusing at least one selected from the group consisting of a nitrogen gas,an inert gas and a liquid as a refrigerant is carried out simultaneouslyin the gettering step.
 79. A method according to claim 73, wherein avicinity of the crystalline semiconductor film is in at least oneselected from the group consisting of a nitrogen (N₂) atmosphere, aninert gas atmosphere, a hydrogen (H₂) atmosphere and a reducing gasatmosphere in the gettering step.
 80. A method according to claim 73,wherein the light source is a light source for emitting at least oneselected from the group consisting of an infrared light and anultraviolet light.
 81. A method according to claim 73, wherein at leastone selected from the group consisting of a halogen lamp, a metal halidelamp, a xenon arc lamp and a reduced pressure mercury lamp is used asthe light source.
 82. A method according to claim 73, wherein the lightsource irradiates a front side of the substrate, a rear side of thesubstrate, or the rear side and the front side of the substrate.
 83. Amethod according to claim 73, wherein the catalytic element comprises atleast one selected from the group consisting of Ni, Fe, Co, Ru, Rh, Pd,Os, Ir, Pt, Cu and Au.
 84. A method according to claim 73, wherein thesemiconductor device is one selected from the group consisting of avideo camera, a digital camera, a front type projector, a rear typeprojector, a head mount display (goggle type display), a personalcomputer, a portable information terminal such as a mobile computer, aportable telephone or an electronic book.
 85. A method according toclaim 73, wherein the impurity element comprises an element selectedfrom group 18 of the periodic table.
 86. A method according to claim 85,wherein the element is selected from Ar, Kr and Xe.
 87. A methodaccording to claim 73, wherein the impurity element comprises a firstelement selected from group 15 of the periodic table, a second elementselected from group 13 of the periodic table and a third elementselected from group 18 of the periodic table.
 88. A method according toclaim 87, wherein the first element is selected from N, P, As, Sb andBi.
 89. A method according to claim 87, wherein the second element isselected from B, Al, Ga, In and Tl.
 90. A method according to claim 87,wherein the third element is selected from Ar, Kr and Xe.
 91. A methodof fabricating a semiconductor device, said method comprising the stepsof: forming an amorphous semiconductor film on an insulating surface;adding a catalytic element being capable of promoting crystallization toa surface of the amorphous semiconductor film; crystallizing theamorphous semiconductor film by controlling a light source to irradiatea pulsed light to the amorphous semiconductor film to form a crystallinesemiconductor film; adding an impurity element to the crystallinesemiconductor film; gettering the catalytic element by controlling thelight source to irradiate the pulsed light to the crystallinesemiconductor film added with the impurity element.
 92. A methodaccording to claim 91, wherein the impurity element comprises an elementselected from group of the periodic table, wherein the element is atleast one selected from the group consisting ot N, P, As, Sb and Bi. 93.A method according to claim 91, wherein the impurity element comprisesat least a first impurity element selected from group 15 of the periodictable and at least a second element selected from group 13 of theperiodic table, wherein the first element is at least one selected fromthe group consisting of N, P, As, Sb and Bi, wherein the second elementis at least one selected from the group consisting of B, Al, Ga, In andTl.
 94. A method according to claim 91, wherein a vicinity of thecrystalline semiconductor film is in at least one selected from thegroup consisting of a nitrogen (N₂) atmosphere, an inert gas atmosphere,a hydrogen (H₂) atmosphere and a reducing gas atmosphere in thecrystallizing and gettering steps.
 95. A method according to claim 91,wherein the catalytic element comprises at least one selected from thegroup consisting of Ni, Fe, Co, Ru, Rh, Pd, Os, Ir, Pt, Cu, and Au. 96.A method according to claim 91, wherein the semiconductor device is oneselected from the group consisting of a video camera, a digital camera,a front type projector, a rear type projector, a head mount display(goggle type display), a personal computer, a portable informationterminal such as a mobile computer, a portable telephone or anelectronic book.
 97. A method of fabricating a semiconductor device,said method comprising the steps of: forming an amorphous semiconductorfilm on an insulating surface; coating a catalytic element being capableof promoting crystallization onto a surface of the amorphoussemiconductor film to form a catalytic element inclusion region;crystallizing the amorphous semiconductor film by controlling a lightsource to irradiate a pulsed light to the amorphous semiconductor filmto form a crystalline semiconductor film; adding an impurity element tothe crystalline semiconductor film; gettering the catalytic element bycontrolling the light source to irradiate the pulsed light to thecrystalline semiconductor film added with the impurity element; forminga semiconductor layer of a desired shape using the crystallinesemiconductor film in which the catalytic element has been gettered;forming a gate insulating film covering the semiconductor layer; forminga gate electrode on the gate insulating film; adding an n-type impurityelement to the semiconductor layer; adding a p-type impurity element toa portion of the semiconductor layer; activating the n-type and p-typeimpurity elements in the semiconductor layer by controlling the lightsource to irradiate a pulsed light, wherein the portion of thesemiconductor layer is an active layer of a p-channel thin filmtransistor.
 98. A method according to claim 97, wherein thecrystallizing step the activating step are carried out in a reducedpressure atmosphere in which an oxygen concentration is reduced byperforming exhaustion by a rotary pump and a mechanical booster pump.99. A method according to claim 97, wherein the impurity elementcomprises an element selected from group 15 of the periodic table,wherein the element is at least one selected from the group consistingof N, P, As, Sb and Bi.
 100. A method according to claim 97, wherein theimpurity element comprises at least a first impurity element selectedfrom group 15 of the periodic table and at least a second elementselected from group 13 of the periodic table, wherein the first elementis at least one selected from the group consisting of N, P, As, Sb andBi, wherein the second element is at least one selected from the groupconsisting of B, Al, Ga, In and Tl.
 101. A method according to claim 97,wherein a vicinity of the crystalline semiconductor film is in at leastone selected from the group consisting of a nitrogen (N₂) atmosphere, aninert gas atmosphere, a hydrogen (H₂) atmosphere and a reducing gasatmosphere in the crystallizing and gettering steps.
 102. A methodaccording to claim 97, wherein the catalytic element comprises at leastone selected from the group consisting of Ni, Fe, Co, Ru, Rh, Pd, Os,Ir, Pt, Cu, and Au.
 103. A method according to claim 97, wherein thesemiconductor device is one selected from the group consisting of avideo camera, a digital camera, a front type projector, a rear typeprojector, a head mount display (goggle type display), a personalcomputer, a portable information terminal such as a mobile computer, aportable telephone or an electronic book.